# data[].attributes.body
Cite our text

# data[].attributes.attachment_link.readable_text
Ask those who've entered the thick of middle age what they think about their mental capacities and you're likely to hear a slew of complaints - their brains don't work as quickly as they used to, they're distractable and unfocused, and they can never remember anyone's name.

While some of these complaints reflect real declines in brain function in our middle years, the deficiencies of a middle-aged brain have likely been overstated by anecdotal evidence and even by some scientific studies.

Contrary to its reputation as a slower, duller version of a youthful brain, it seems that the middle-aged mind not only maintains many of the abilities of youth but actually acquires some new ones. The adult brain seems to be capable of rewiring itself well into middle age, incorporating decades of experiences and behaviors. Research suggests, for example, the middle-aged mind is calmer, less neurotic and better able to sort through social situations. Some middle-agers even have improved cognitive abilities.

"There is an enduring potential for plasticity, reorganization and preservation of capacities," says cognitive neuroscientist Patricia Reuter-Lorenz, PhD, of the University of Michigan in Ann Arbor.

Researchers now have an unprecedented wealth of data on the aging brain from the Seattle Longitudinal Study, which has tracked the cognitive abilities of thousands of adults over the past 50 years. These results show that middle-aged adults perform better on four out of six cognitive tests than those same individuals did as young adults, says study leader Sherry Willis, PhD, of the University of Washington in Seattle.

While memorization skills

and perceptual speed both start to decline in young adulthood, verbal abilities, spatial reasoning, simple math abilities and abstract reasoning skills all improve in middle age.

Cognitive skills in the aging brain have also been studied extensively in pilots and air-traffic controllers. Again, older pilots show declines in processing speed and memory capacity, but their overall performance seems to remain intact. In a study published in Neurology (Vol. 68, No. 9) in 2007, researchers tested pilots age 40 to 69 as they performed on flight simulators. Older pilots took longer to learn to use the simulators but did a better job than their younger colleagues at achieving their objective: avoiding collisions.

Many middle-aged people are convinced that they're just not as mentally skilled or even as intelligent as they used to be, Willis says. But it's possible that's an illusion arising from the aspects of cognition that do suffer in middle age.

"They may get the sense they're cognitively slow just because they're perceptually slow or slow with psychomotor skills," she says, when in reality their brains are performing most tasks remarkably well.

Changing strategies

Researchers used to believe that brain activity would slow down with aging so that older brains would show less activity overall than younger ones. But functional neuroimaging studies have overturned that assumption.

For example, psychologist Cheryl Grady, PhD, of the University of Toronto, and her colleagues have found that older adults use more of their brains than young adults to accomplish certain tasks. In a study published in the Journal of Neuroscience (Vol. 3, No. 2) in 1994, Grady reported that performing a face-matching task activates mainly the occipital visual areas in younger adults, but older adults use these areas as well as the prefrontal cortex. (Both groups of adults are equally skilled at the task.)

Several groups, including Grady's, have also found that older adults tend to use both brain hemispheres for tasks that only activate one hemisphere in younger adults. Younger adults show similar bilateralization of brain activity if the task is difficult enough, Reuter-Lorenz says, but older adults use both hemispheres at lower levels of difficulty.

The strategy seems to work. According to work published in Neuroimage (Vol. 17, No. 3) in 2002, the best-performing older adults are the most likely to show this bilateralization. Older adults who continue to use only one hemisphere don't perform as well.

Reuter-Lorenz finds these changes with age encouraging, as they show that the middle-aged brain is capable of altering how it does things in order to accomplish the task at hand. "Compensation through some brain mechanisms may make up for losses in others," she says.

Grady cautions that many studies on the middle-aged brain are preliminary, as this age group "hasn't been studied very much. It certainly hasn't been studied enough." Most functional imaging studies, for example, tend to recruit college students and retirees as study subjects, Grady says. Cognitive characteristics of in-between ages are often simply extrapolated from the two ends of the spectrum.

While a linear continuum may be accurate for many traits, it may not always be a valid assumption. Grady's own work on brain activation during memory tasks, for example, suggests that the middle-aged pattern does fall between those of a young adult and an elderly person.

For example, the amount of white matter in the brain, which forms the connections among nerve cells, seems to increase until age 40 or 50 and then falls off again. "So that suggests that there are some developmental changes that really don't hit their peak until somewhere in middle age," Grady says.

At least the glasses are rose-colored

Emotions and social interactions - even personality - may systematically change as people enter middle age. Many studies have found that people become calmer and less neurotic as they age. "There's a quieting of emotional storms," Reuter-Lorenz says.

Work by cognitive psychologist Mara Mather, PhD, of the University of Southern California in Los Angeles, has found that older adults tend to focus more on positive information and less on negative information than their younger counterparts. In 2004, she and her colleagues reported in Psychological Science (Vol. 15, No. 4) that the amygdala in older adults actually responds less to negative stimuli (such as unpleasant pictures) than it does in young adults. Starting around age 40, people also show a better memory for positive images than for negative ones, and this trend continues until at least age 80.

This "positivity effect" is seen even more strongly in people who are doing exceptionally well cognitively, Mather says, "so it doesn't seem to be something that just goes along with cognitive decline; it seems to be something that's an active process."

These findings fit with many self-reports from middle-aged and older individuals, Mather says. Older adults rank emotional stability and positive affect as more important than younger adults do, and they say that they're better at regulating their own emotions than they were in their youth.

Although scientifically analyzing such qualities as judgment and wisdom is considerably more difficult than measuring psychomotor speed or memory storage capacity, some researchers are trying to do just that. Research over the past several years has reported that middle-aged people are much more expert at many social interactions - such as judging the true intentions of other human beings - than are those either younger or older.

And work by David Laibson, PhD, at Harvard University, found that adults in midlife show better economic understanding and make better financial decisions than either younger or older adults. In fact, the average person's financial judgment seems to peak at 53.

Variability and influences

One of the middle-aged mind's most striking features may not be any one feature or ability, but rather the variation in cognitive skills that's found in this age group. Although differences in cognition obviously exist among individuals at all ages, these differences seem to increase in middle age.

For example, memory and attention frequently suffer in middle age, but some individuals' abilities actually improve in midlife. In Willis's Seattle study, most participants' ability to remember lists of words declined in middle age, but about 15 percent performed better on this task than they did as young adults.

"If you study a wide range of abilities, you begin to realize how very complex cognitive decline is and how many individual differences there are," Willis says.

This variation in behavioral performance is also reflected in expression of genes related to learning and memory. In a study published in Nature in 2004 (Vol. 429, No. 6,994), the brains of adults under age 40 consistently showed little damage and high levels of expression of these genes, while brains from those over 73 showed lots of damage and low gene expression. But in the middle-aged group, results varied widely. Some middle-aged brains were already shutting down, whereas others were indistinguishable from a 30-year-old brain.

"It's a very interesting and heterogeneous group," Grady says.

With more study of middle age in general - especially of those who seem to glide through those years with cognitive abilities intact or even improving - scientists hope to enable many more people to preserve cognitive health into old age.

So far, research suggests that remaining cognitively impressive with age comes from adopting certain behaviors as well as possessing some genetic luck, Willis says. For example, researchers have identified several gene variants that are risk factors for early memory problems. But people who show cognitive improvement in midlife also tend to be more physically, cognitively and socially active than those who don't fare as well.

"Instead of a crisis, middle age should be thought of as a time for a new form of self-investment," Reuter-Lorenz says. "This time of life brings so many new opportunities to invest in your own cognitive and physical resources, so you can buffer against the effects of older age."
Melissa Lee Phillips is a writer in Seattle.

# data[].attributes.attachment_link.description
Ask those who've entered the thick of middle age what they think about their mental capacities and you're likely to hear a slew of complaints - their brains don't work as quickly as they used to, they're distractable and unfocused, and they can never remember anyone's name.

# data[].attributes.headline
Neuroscience Of 20-Somethings: ‘Emerging Adults’ Show Brain Differences

# data[].attributes.subject
Neuroscience Of 20-Somethings: ‘Emerging Adults’ Show Brain Differences

# data[].attributes.attachment_link.readable_text
In the opening scene of Lena Dunham's HBO series Girls, the Horvaths tell their 24-year-old daughter Hannah that they will no longer support her-or, as her mother puts it: "No. More. Money." A recent college graduate, Hannah has been living in Brooklyn, completing an unpaid internship and working on a series of personal essays. The Horvaths intend to give Hannah "one final push" toward, presumably, a lifestyle that more closely resembles adulthood. Hannah protests. Her voice quavers. She tells her parents that she does not want to see them the following day, even though they are leaving town soon: "I have work and then I have a dinner thing and then I am busy-trying to become who I am."

Across the United States-and in developed nations around the world-twenty-somethings like Hannah are taking longer to finish school, leave home, begin a career, get married and reach other milestones of adulthood. These trends are not just anecdotal; sociologists and psychologists have gathered supporting data. Robin Marantz Henig summarizes the patterns in her 2010 New York Times Magazine feature:

"One-third of people in their 20s move to a new residence every year. Forty percent move back home with their parents at least once. They go through an average of seven jobs in their 20s, more job changes than in any other stretch. Two-thirds spend at least some time living with a romantic partner without being married. And marriage occurs later than ever. The median age at first marriage in the early 1970s, when the baby boomers were young, was 21 for women and 23 for men; by 2009 it had climbed to 26 for women and 28 for men, five years in a little more than a generation."

These demographic shifts have transformed the late teens through mid twenties into a distinct stage of life according to Jeffrey Arnett of Clark University, who calls the new phase "emerging adulthood." Arnett acknowledges that emerging adulthood is relevant only to about 18 percent of the global population, to certain groups of twenty-somethings in developed nations such as the United States, Canada, Western Europe, Japan and Australia. To make some broad generalizations, people living in the rest of world-particularly in developing countries-are much more likely to finish formal education in their teens and marry by their early twenties.

Although Arnett primarily studies how society, culture and the economy have created emerging adulthood, some scientists and journalists have wondered whether biology is involved as well. Henig writes that some researchers think a lengthy preamble to adulthood might be "better-suited to our neurological hard-wiring" and that the general ambivalence of twenty-somethings-feeling that they are sort of adults, but not really adults- "reflects what is going on in the brain, which is also both grown-up and not-quite-grown-up." Most recently, The Wall Street Journal ran an article recommending that concerned parents of twenty-somethings should "chill out" because "recent research into how the brain develops suggests that people are better equipped to make major life decisions in their late 20s than earlier in the decade. The brain, once thought to be fully grown after puberty, is still evolving into its adult shape well into a person's third decade, pruning away unused connections and strengthening those that remain, scientists say."

After reading The Wall Street Journal article, a flock of questions began flapping in my own twenty-something mind. What does it mean to have a "fully grown" adult brain anyways and, if my peers and I do not yet have such a brain, exactly how un-grown-up are our noggins, how uncooked our noodles? Were we neurologically unfit to make the important decisions about careers and marriage that some of us have already made? If emerging adulthood is itself an emerging phenomenon, what is its precise relationship to the biology of an organ whose defining characteristics began evolving millions of years ago? And does a Peter Pan brain have any redeeming qualities?

In an ongoing study that kicked off in 1991, Jay Giedd of the National Institute of Mental Health has been tracking the brain development of nearly 4,000 people ranging in age from a few days to 96 years. Every two years, Giedd invites his volunteers to the lab to scan their brains with magnetic resonance imaging (MRI). Giedd and his colleagues have learned that, contrary to neuroscientists' earliest assumptions, the brain continues to markedly rewire itself even after puberty.

Between 12 and 25, the brain changes its structure in a few important ways. Like an overeager forest, neurons in the early adolescent brain become bushier, growing more and more overlapping branches whose twigs reach toward one another, nearly touching except for tiny gaps known as synapses. When an electrical impulse-or action potential-reaches a twig, the neuron flings spurts of chemical messages across the synapse. Over time, depending on how teens busy their minds, twigs around the least used synapses wither, while twigs flanking the most trafficked synapses grow thicker, strengthening those connections. Meanwhile, as neurons in the adolescent brain make and break connections, glia-non-firing brain cells-set to work wrapping neurons in a fatty white tissue known as myelin, considerably increasing the speed at which electrical impulses travel along neurons' branches.

Although these developmental changes continue far longer than researchers initially thought, they are not as dramatic in the twenties as they are in the teens. "In the twenties, the brain is definitely still changing, but it's not rampant biological change," explains Beatriz Luna of the University of Pittsburgh. "Most of the brain's systems are good to go in one's twenties." In an email message, B.J. Casey of Weill Cornell Medical College made a similar remark: "Most of my functional imaging work shows the greatest brain changes between 13 and 17 with relative stability across 20s."

In her own studies, Luna has found that, at least on certain cognitive tasks, people in their early twenties perform just as well as people in their late twenties. She often asks her volunteers to deliberately look away from a flashing light on a screen-a test of impulse inhibition, since flickers attract our attention. "Ten-year-olds stink at it, failing about 45 percent of the time," as David Dobbs put it in his National Geographic feature. "Teens do much better. In fact, by age 15 they can score as well as adults if they're motivated, resisting temptation about 70 to 80 percent of the time...And by age 20, their brains respond to this task much as the adults' do."

In Luna's studies, brain behavior changed in parallel with improving scores. Older volunteers showed higher activity in brain regions involved in identifying errors, such as the anterior cingulate cortex. Related research has shown that older adolescents have stronger bridges of neural tissue connecting the emotional and motor centers of their brains with the prefrontal cortex, an "executive" brain region known for, among many other things, inhibiting impulses and tempering bubbling emotions. Luna and other researchers now think that, more than the growth of any single brain region, this increasing interconnectedness characterizes brain development in the twenties. Of course, that doesn't mean that once someone leaves behind their twenties they will never again lose their cool or act thoughtlessly instead of prudently. Individual variation makes all the difference. Some teens and twenty-somethings are simply more cautious and composed than some adults.

To reflect the ongoing structural changes in the adolescent and twenty-something brain, many journalists and scientists use words and phrases like "unfinished," "work in progress," "under construction" and "half-baked." Such language implies that the brain eventually reaches a kind of ideal state when it is "done." But there is no final, optimal state. The human brain is not a soufflé that gradually expands over time and finally finishes baking at age 30. Yes, we can identify and label periods of dramatic development-or windows of heightened plasticity-but that should not eclipse the fact that brain changes throughout life.

Studies have confirmed, for example, that London taxicab drivers grow larger hippocampi as they learn to navigate London's convoluted roadways. This growth in the hippocampus, a brain region essential for forming new memories, is not explained by youth: According to the Public Carriage Office, 98 per cent of London taxi drivers are over the age of 30 [PDF]. Granted, the hippocampus is one of only two regions thought to grow new neurons in adulthood, but the brain remains remarkably plastic in other ways too. When one part of the brain shrivels-say, from stroke or traumatic injury- nearby regions often adopt their deceased neighbor's functions. When blind people learn to use echolocation, areas of their brains usually devoted to vision learn to interpret the echoes of clicks and taps instead. Neuroplasticity is an everyday phenomenon as well. The adult brain constantly strengthens and weakens connections between its cells. In fact, learning and memory are dependent on such flexibility. Learning a new language or picking up an instrument may be easier when one is young, but adaptability and creativity do not expire on one's 30th birthday.
Brains of our past and present
Mapping structural changes in the brain over time tells us how the brain matures, but not why it matures that way. To answer why we have to think about the benefits that prolonged brain development would have offered our ancestors. After all, the human brain's fundamental phases of development could not have popped into existence in the last 50 years or even thousands of years ago-more likely, they evolved at least a couple million years ago in the Paleolithic, when the human brain began to increase in size and morph into the organ we know today. Keeping the brain extra flexible for a longer period of time may have provided our ancestors with more opportunities to quickly master new skills and adapt to a changing environment. But taking too long to learn how to manage emotions, control impulses and plan ahead may also have impeded survival.

Painting an accurate tableau of the Paleolithic lifestyle is difficult because the evidence is scant, but we can say a few things with confidence. First, although the exact lifespans of early humans are not certain, evidence from the fossil record-as well as death rates among modern hunter-gatherer societies-suggests that most early humans did not live as long as people in developed nations today. Children frequently died in their first years of life. If you made it to 15, you were more likely to live at least another 15 or 20 years, but people who lived past their forties were probably in a minority. Second, early humans likely started having children far sooner than people in industrialized countries today. Paleolithic twenty-somethings, we can safely assume, did not have the luxury of spending a few years after college "finding themselves" while backpacking through India and volunteering on organic farms. Rather, people who survived to their twenties in the Paleolithic probably had to bear the responsibilities of parenthood as well as contribute substantially to their community's survival. These are not exactly circumstances that favor leisurely cognitive development late into one's twenties.

When I described this scenario to Giedd, however, he suggested that widening the window of heightened neuroplasticity to encompass one's twenties may have helped Homo sapiens adapt to rapid shifts in the climate. Unfortunately, as with many hypothesis in evolutionary psychology, scientists do not have a way to objectively test these ideas. Still, if we want to fully understand the brain, we cannot ignore the fact that it evolved in circumstances very different from our own.

For now, let's put the brains of ancient twenty-somethings out of our minds. What about the twenty-somethings of today? Even if the brain's developmental changes are more dramatic in the teens than in the twenties, the best available evidence suggests that a twenty-something's brain boasts a little more adaptability than an older brain. Our twenties might represent a final opportunity to begin mastering a particular skill with a kind of facility we cannot enjoy in later decades. Should people in their twenties buckle down and choose something, anything, to practice while their brains are still nimble? Does the neuroscience suggest that, for all their freedom and fun, gallivanting twenty-somethings neglect their last years of heightened plasticity? Should parents encourage their 20-year-olds to shirk adult responsibilities lest they hamper an advantageous period of self-discovery and wild experimentation?

Solid neuroscience that can directly answer questions like does not yet exist. "It's too soon to tell," Giedd says, "but we're wondering." He and his colleagues plan to compare the brain development of girls who become pregnant in their teens to girls who do not. "Teen pregnancy changes all your priorities and what you do with your time-how do those experiences change the brain?" Arnett agrees that such neuroimaging studies would be useful. "Even in industrialized countries, a lot of people still get married pretty early. You could do brain studies comparing people who experience their twenties differently and contrast how their brains develop."

In the meantime, twenty-somethings can expect increasingly frequent waves of sage advice from academics, bloggers and concerned parents alike. "Watching talking cats on YouTube isn't as good for cognitive development as reading or taking classes," Laurence Steinberg of Temple University told The Wall Street Journal. Truth. In the same article, Jennifer Tanner, co-chair of the Society for the Study of Emerging Adulthood, provides her own pearl: "My advice is, if your parents are currently doing things for you that you could do for yourself, take the controls. Say, 'No. Mom, Let me get my own shampoo.'" Thanks for the tip, Ms. Tanner. I mean, if I were living at home to save money, I wouldn't mind sharing the jumbo size 2-in-1 shampoo and conditioner with my siblings. But I'm pretty sure the vast majority of my peers have a handle on shampoo selection by now. Because we're worth it.

Emerging adulthood is real-it's happening, albeit to a small percentage of the world's population. Whether we can, at this moment in time, meaningfully link this life stage to neuroscience seems a tenuous proposition at best. By itself, brain biology does not dictate who we are. The members of any one age group are not reducible to a few distinguishing structural changes in the brain. Ultimately, the fact that a twenty-something has weaker bridges between various brain regions than someone in their thirties is not hugely important-it's just one aspect of a far more complex identity.

BEFORE YOU GO

# data[].attributes.attachment_link.title
What's Different About Brains Of 20-Somethings?

# data[].attributes.attachment_link.description
In the opening scene of Lena Dunham's HBO series Girls, the Horvaths tell their 24-year-old daughter Hannah that they will no longer support her-or, as her mother puts it: "No. More. Money." A recent college graduate, Hannah has been living in Brooklyn, completing an unpaid internship and working on a series of personal essays.

# data[].attributes.body
This assignment will require you to type directly in this worksheet. Part I will require you to research cognitive related changes during adulthood. In each box, describe 3-4 cognitive changes that generally occur during that age-range (include things such as memory, attention, structural change, processing speed, executive functioning, and neurotransmission).

A minimum of three resources are required. Your textbook may serve as one resource. Make sure the references are current and cited both with your chart and referenced in the reference section.

I’ll be looking to see that you understand the roles that the different brain regions have. You need to include research AND your own thoughts or examples.

# data[].attributes.body
Cite our Text

# data[].attributes.headline
What's Different About Brains of 20 Somethings

# data[].attributes.subject
What's Different About Brains of 20 Somethings

# data[].attributes.attachment_link.readable_text
In the opening scene of Lena Dunham's HBO series Girls, the Horvaths tell their 24-year-old daughter Hannah that they will no longer support her-or, as her mother puts it: "No. More. Money." A recent college graduate, Hannah has been living in Brooklyn, completing an unpaid internship and working on a series of personal essays. The Horvaths intend to give Hannah "one final push" toward, presumably, a lifestyle that more closely resembles adulthood. Hannah protests. Her voice quavers. She tells her parents that she does not want to see them the following day, even though they are leaving town soon: "I have work and then I have a dinner thing and then I am busy-trying to become who I am."

Across the United States-and in developed nations around the world-twenty-somethings like Hannah are taking longer to finish school, leave home, begin a career, get married and reach other milestones of adulthood. These trends are not just anecdotal; sociologists and psychologists have gathered supporting data. Robin Marantz Henig summarizes the patterns in her 2010 New York Times Magazine feature:

"One-third of people in their 20s move to a new residence every year. Forty percent move back home with their parents at least once. They go through an average of seven jobs in their 20s, more job changes than in any other stretch. Two-thirds spend at least some time living with a romantic partner without being married. And marriage occurs later than ever. The median age at first marriage in the early 1970s, when the baby boomers were young, was 21 for women and 23 for men; by 2009 it had climbed to 26 for women and 28 for men, five years in a little more than a generation."

These demographic shifts have transformed the late teens through mid twenties into a distinct stage of life according to Jeffrey Arnett of Clark University, who calls the new phase "emerging adulthood." Arnett acknowledges that emerging adulthood is relevant only to about 18 percent of the global population, to certain groups of twenty-somethings in developed nations such as the United States, Canada, Western Europe, Japan and Australia. To make some broad generalizations, people living in the rest of world-particularly in developing countries-are much more likely to finish formal education in their teens and marry by their early twenties.

Although Arnett primarily studies how society, culture and the economy have created emerging adulthood, some scientists and journalists have wondered whether biology is involved as well. Henig writes that some researchers think a lengthy preamble to adulthood might be "better-suited to our neurological hard-wiring" and that the general ambivalence of twenty-somethings-feeling that they are sort of adults, but not really adults- "reflects what is going on in the brain, which is also both grown-up and not-quite-grown-up." Most recently, The Wall Street Journal ran an article recommending that concerned parents of twenty-somethings should "chill out" because "recent research into how the brain develops suggests that people are better equipped to make major life decisions in their late 20s than earlier in the decade. The brain, once thought to be fully grown after puberty, is still evolving into its adult shape well into a person's third decade, pruning away unused connections and strengthening those that remain, scientists say."

After reading The Wall Street Journal article, a flock of questions began flapping in my own twenty-something mind. What does it mean to have a "fully grown" adult brain anyways and, if my peers and I do not yet have such a brain, exactly how un-grown-up are our noggins, how uncooked our noodles? Were we neurologically unfit to make the important decisions about careers and marriage that some of us have already made? If emerging adulthood is itself an emerging phenomenon, what is its precise relationship to the biology of an organ whose defining characteristics began evolving millions of years ago? And does a Peter Pan brain have any redeeming qualities?

In an ongoing study that kicked off in 1991, Jay Giedd of the National Institute of Mental Health has been tracking the brain development of nearly 4,000 people ranging in age from a few days to 96 years. Every two years, Giedd invites his volunteers to the lab to scan their brains with magnetic resonance imaging (MRI). Giedd and his colleagues have learned that, contrary to neuroscientists' earliest assumptions, the brain continues to markedly rewire itself even after puberty.

Between 12 and 25, the brain changes its structure in a few important ways. Like an overeager forest, neurons in the early adolescent brain become bushier, growing more and more overlapping branches whose twigs reach toward one another, nearly touching except for tiny gaps known as synapses. When an electrical impulse-or action potential-reaches a twig, the neuron flings spurts of chemical messages across the synapse. Over time, depending on how teens busy their minds, twigs around the least used synapses wither, while twigs flanking the most trafficked synapses grow thicker, strengthening those connections. Meanwhile, as neurons in the adolescent brain make and break connections, glia-non-firing brain cells-set to work wrapping neurons in a fatty white tissue known as myelin, considerably increasing the speed at which electrical impulses travel along neurons' branches.

Although these developmental changes continue far longer than researchers initially thought, they are not as dramatic in the twenties as they are in the teens. "In the twenties, the brain is definitely still changing, but it's not rampant biological change," explains Beatriz Luna of the University of Pittsburgh. "Most of the brain's systems are good to go in one's twenties." In an email message, B.J. Casey of Weill Cornell Medical College made a similar remark: "Most of my functional imaging work shows the greatest brain changes between 13 and 17 with relative stability across 20s."

In her own studies, Luna has found that, at least on certain cognitive tasks, people in their early twenties perform just as well as people in their late twenties. She often asks her volunteers to deliberately look away from a flashing light on a screen-a test of impulse inhibition, since flickers attract our attention. "Ten-year-olds stink at it, failing about 45 percent of the time," as David Dobbs put it in his National Geographic feature. "Teens do much better. In fact, by age 15 they can score as well as adults if they're motivated, resisting temptation about 70 to 80 percent of the time...And by age 20, their brains respond to this task much as the adults' do."

In Luna's studies, brain behavior changed in parallel with improving scores. Older volunteers showed higher activity in brain regions involved in identifying errors, such as the anterior cingulate cortex. Related research has shown that older adolescents have stronger bridges of neural tissue connecting the emotional and motor centers of their brains with the prefrontal cortex, an "executive" brain region known for, among many other things, inhibiting impulses and tempering bubbling emotions. Luna and other researchers now think that, more than the growth of any single brain region, this increasing interconnectedness characterizes brain development in the twenties. Of course, that doesn't mean that once someone leaves behind their twenties they will never again lose their cool or act thoughtlessly instead of prudently. Individual variation makes all the difference. Some teens and twenty-somethings are simply more cautious and composed than some adults.

To reflect the ongoing structural changes in the adolescent and twenty-something brain, many journalists and scientists use words and phrases like "unfinished," "work in progress," "under construction" and "half-baked." Such language implies that the brain eventually reaches a kind of ideal state when it is "done." But there is no final, optimal state. The human brain is not a soufflé that gradually expands over time and finally finishes baking at age 30. Yes, we can identify and label periods of dramatic development-or windows of heightened plasticity-but that should not eclipse the fact that brain changes throughout life.

Studies have confirmed, for example, that London taxicab drivers grow larger hippocampi as they learn to navigate London's convoluted roadways. This growth in the hippocampus, a brain region essential for forming new memories, is not explained by youth: According to the Public Carriage Office, 98 per cent of London taxi drivers are over the age of 30 [PDF]. Granted, the hippocampus is one of only two regions thought to grow new neurons in adulthood, but the brain remains remarkably plastic in other ways too. When one part of the brain shrivels-say, from stroke or traumatic injury- nearby regions often adopt their deceased neighbor's functions. When blind people learn to use echolocation, areas of their brains usually devoted to vision learn to interpret the echoes of clicks and taps instead. Neuroplasticity is an everyday phenomenon as well. The adult brain constantly strengthens and weakens connections between its cells. In fact, learning and memory are dependent on such flexibility. Learning a new language or picking up an instrument may be easier when one is young, but adaptability and creativity do not expire on one's 30th birthday.
Brains of our past and present
Mapping structural changes in the brain over time tells us how the brain matures, but not why it matures that way. To answer why we have to think about the benefits that prolonged brain development would have offered our ancestors. After all, the human brain's fundamental phases of development could not have popped into existence in the last 50 years or even thousands of years ago-more likely, they evolved at least a couple million years ago in the Paleolithic, when the human brain began to increase in size and morph into the organ we know today. Keeping the brain extra flexible for a longer period of time may have provided our ancestors with more opportunities to quickly master new skills and adapt to a changing environment. But taking too long to learn how to manage emotions, control impulses and plan ahead may also have impeded survival.

Painting an accurate tableau of the Paleolithic lifestyle is difficult because the evidence is scant, but we can say a few things with confidence. First, although the exact lifespans of early humans are not certain, evidence from the fossil record-as well as death rates among modern hunter-gatherer societies-suggests that most early humans did not live as long as people in developed nations today. Children frequently died in their first years of life. If you made it to 15, you were more likely to live at least another 15 or 20 years, but people who lived past their forties were probably in a minority. Second, early humans likely started having children far sooner than people in industrialized countries today. Paleolithic twenty-somethings, we can safely assume, did not have the luxury of spending a few years after college "finding themselves" while backpacking through India and volunteering on organic farms. Rather, people who survived to their twenties in the Paleolithic probably had to bear the responsibilities of parenthood as well as contribute substantially to their community's survival. These are not exactly circumstances that favor leisurely cognitive development late into one's twenties.

When I described this scenario to Giedd, however, he suggested that widening the window of heightened neuroplasticity to encompass one's twenties may have helped Homo sapiens adapt to rapid shifts in the climate. Unfortunately, as with many hypothesis in evolutionary psychology, scientists do not have a way to objectively test these ideas. Still, if we want to fully understand the brain, we cannot ignore the fact that it evolved in circumstances very different from our own.

For now, let's put the brains of ancient twenty-somethings out of our minds. What about the twenty-somethings of today? Even if the brain's developmental changes are more dramatic in the teens than in the twenties, the best available evidence suggests that a twenty-something's brain boasts a little more adaptability than an older brain. Our twenties might represent a final opportunity to begin mastering a particular skill with a kind of facility we cannot enjoy in later decades. Should people in their twenties buckle down and choose something, anything, to practice while their brains are still nimble? Does the neuroscience suggest that, for all their freedom and fun, gallivanting twenty-somethings neglect their last years of heightened plasticity? Should parents encourage their 20-year-olds to shirk adult responsibilities lest they hamper an advantageous period of self-discovery and wild experimentation?

Solid neuroscience that can directly answer questions like does not yet exist. "It's too soon to tell," Giedd says, "but we're wondering." He and his colleagues plan to compare the brain development of girls who become pregnant in their teens to girls who do not. "Teen pregnancy changes all your priorities and what you do with your time-how do those experiences change the brain?" Arnett agrees that such neuroimaging studies would be useful. "Even in industrialized countries, a lot of people still get married pretty early. You could do brain studies comparing people who experience their twenties differently and contrast how their brains develop."

In the meantime, twenty-somethings can expect increasingly frequent waves of sage advice from academics, bloggers and concerned parents alike. "Watching talking cats on YouTube isn't as good for cognitive development as reading or taking classes," Laurence Steinberg of Temple University told The Wall Street Journal. Truth. In the same article, Jennifer Tanner, co-chair of the Society for the Study of Emerging Adulthood, provides her own pearl: "My advice is, if your parents are currently doing things for you that you could do for yourself, take the controls. Say, 'No. Mom, Let me get my own shampoo.'" Thanks for the tip, Ms. Tanner. I mean, if I were living at home to save money, I wouldn't mind sharing the jumbo size 2-in-1 shampoo and conditioner with my siblings. But I'm pretty sure the vast majority of my peers have a handle on shampoo selection by now. Because we're worth it.

Emerging adulthood is real-it's happening, albeit to a small percentage of the world's population. Whether we can, at this moment in time, meaningfully link this life stage to neuroscience seems a tenuous proposition at best. By itself, brain biology does not dictate who we are. The members of any one age group are not reducible to a few distinguishing structural changes in the brain. Ultimately, the fact that a twenty-something has weaker bridges between various brain regions than someone in their thirties is not hugely important-it's just one aspect of a far more complex identity.

BEFORE YOU GO

# data[].attributes.attachment_link.title
What's Different About Brains Of 20-Somethings?

# data[].attributes.attachment_link.description
In the opening scene of Lena Dunham's HBO series Girls, the Horvaths tell their 24-year-old daughter Hannah that they will no longer support her-or, as her mother puts it: "No. More. Money." A recent college graduate, Hannah has been living in Brooklyn, completing an unpaid internship and working on a series of personal essays.

# data[].attributes.body
Requires that you answer the follow-up questions.

# data[].attributes.body
The Teen Brain: Still Under Construction

# data[].attributes.attachment_link.title
Publications about Brain Anatomy and Physiology

# data[].attributes.attachment_link.description
Lists NIMH Publications about Brain Anatomy and Physiology.

# data[].attributes.attachment_link.readable_text
Abstract

Ageing causes changes to the brain size, vasculature, and cognition. The brain shrinks with increasing age and there are changes at all levels from molecules to morphology. Incidence of stroke, white matter lesions, and dementia also rise with age, as does level of memory impairment and there are changes in levels of neurotransmitters and hormones. Protective factors that reduce cardiovascular risk, namely regular exercise, a healthy diet, and low to moderate alcohol intake, seem to aid the ageing brain as does increased cognitive effort in the form of education or occupational attainment. A healthy life both physically and mentally may be the best defence against the changes of an ageing brain. Additional measures to prevent cardiovascular disease may also be important.

Keywords: ageing, brain, cognition

The effects of ageing on the brain and cognition are widespread and have multiple aetiologies. Ageing has its effects on the molecules, cells, vasculature, gross morphology, and cognition. As we age our brains shrink in volume, particularly in the frontal cortex. As our vasculature ages and our blood pressure rises the possibility of stroke and ischaemia increases and our white matter develops lesions. Memory decline also occurs with ageing and brain activation becomes more bilateral for memory tasks. This may be an attempt to compensate and recruit additional networks or because specific areas are no longer easily accessed. Genetics, neurotransmitters, hormones, and experience all have a part to play in brain ageing. But, it is not all negative, higher levels of education or occupational attainment may act as a protective factor. Also protective are a healthy diet, low to moderate alcohol intake, and regular exercise. Biological ageing is not tied absolutely to chronological ageing and it may be possible to slow biological ageing and even reduce the possibility of suffering from age related diseases such as dementia.

Physical changes

Cognitive change

The most widely seen cognitive change associated with ageing is that of memory. Memory function can be broadly divided into four sections, episodic memory, semantic memory, procedural memory, and working memory.18 The first two of these are most important with regard to ageing. Episodic memory is defined as "a form of memory in which information is stored with 'mental tags', about where, when and how the information was picked up".19 An example of an episodic memory would be a memory of your first day at school, the important meeting you attended last week, or the lesson where you learnt that Paris is the capital of France. Episodic memory performance is thought to decline from middle age onwards. This is particularly true for recall in normal ageing and less so for recognition.20 It is also a characteristic of the memory loss seen in Alzheimer's disease (AD).18

Semantic memory is defined as "memory for meanings", for example, knowing that Paris is the capital of France, that 10 millimetres make up a centimetre, or that Mozart composed the Magic Flute.19 Semantic memory increases gradually from middle age to the young elderly but then declines in the very elderly.20 It is not yet clear why these changes occur and it has been hypothesised that the very elderly have less resources to draw on and that their performance may be affected in some tasks by slower reaction times, lower attentional levels, slower processing speeds, detriments in sensory and or perceptual functions, or potentially a lesser ability to use strategies.20,21,22,23

There have been studies investigating different types of memory in ageing using neuropsychological testing and neuroimaging. However, it must be pointed out that it is sometimes methodologically difficult to separate some of these functions, for example episodic memory encoding and semantic memory retrieval.24 Despite this studies are beginning to examine performance on memory tasks with ageing and by neuroimaging. A review article focusing in this area highlighted the changes in regional brain activation.24 Older brains tend to show more symmetrical activation, either because they have increased activation in a hemisphere that is less activated than in younger adults or because they show reduced activation in the areas most activated in younger adults. This has been shown for visual perception and in memory tasks.24 The observed changes in activation in the left and right prefrontal cortex are in keeping with changes in memory performance, particularly episodic memory, as this is thought to be based in this area.24 It has also been suggested that the actual level of brain activation, as shown in neuroimaging, may be related more directly to the levels of memory performance.25 A review of studies using electroencephalograms to examine event related potentials in response to stimuli also contribute some support for increased symmetry in brain activation with age.26

The increased symmetrical hemispheric activation is a robust finding and has been referred to as HAROLD or hemispheric asymmetry reduction in older adults. It is not clear whether this change is an attenuation of the response seen in younger subjects, an inability to recruit specific areas, or an attempt to compensate for the ageing process.21,23,25 This change in activation occurring in the frontal lobes fits with changes in memory performance and with the possible white matter changes referred to above, however, other factors such as changes in neurotransmitter or hormone levels also require consideration.

Mechanisms of change

Another factor to consider with regard to the ageing brain and its cognitive performance is hormonal influence. It is known that sex hormones can affect cognitive processes in adulthood and that changes in sex hormones occur in ageing particularly in women at menopause. Women also have a higher incidence of AD even when longer life expectancy is taken into account.14 AD is characterised by failing memory and there has been a suggestion that oestrogen therapy may increase dopaminergic responsivity32 and play a protective part in AD.33,34 It must be remembered though that the use of HRT has recently been shown to have cancer risks.35 Growth hormone levels also decline with age and may be associated with cognitive performance although the evidence is far from clear.36

The ageing brain may also suffer from impaired glucose metabolism20 or a reduced input of glucose or oxygen as cerebrovascular efficiency falls, although reduction in glucose may partly be attributable to atrophy rather than any change in glucose metabolism.37 Change in vasculature is important and another common finding in elderly brains related to ischaemia are white matter lesions and stroke.

Vascular factors and dementia

Increasing evidence points to vascular factors not only contributing to cognitive problems in ageing but also to the two most common dementias seen in this population. The prevalence of dementia increases almost exponentially with increasing age with around 20% of those aged 80 affected rising to 40% of those aged 90.39

Protective factors

Conclusion

That the brain changes with increasing chronological age is clear, however, less clear is the rate of change, the biological age of the brain, and the processes involved. The brain changes that may affect cognition and behaviour occur at the levels of molecular ageing, intercellular and intracellular ageing, tissue ageing, and organ change. There are many areas of research under investigation to elucidate the mechanisms of ageing and to try to alleviate age associated disorders, particularly dementias that have the biggest impact on the population. In terms of personal brain ageing the studies suggest that a healthy lifestyle that reduces cardiovascular risk will also benefit the brain. Medical care in this area may even offer limited protection in terms of cognitive decline but this needs to be shown for antihypertensives, antiplatelet, and anticholesterol agents. It is also important to take note of the limitations in studies on the ageing brain. Many studies are cross sectional in nature, have small numbers of participants with wide ranges in chronological age, lack control for risk factors or protective factors, take no account of education that may improve performance on cognitive tests, and finally lack assessment with regard to depression that may also affect performance. It must be remembered that the brains of an elderly group may show cohort effects related to wider environmental influences, for example, lack of high energy foods while growing up.2 It is also extremely difficult to separate out and measure single cognitive processes to fully understand any changes.106

Future studies need to take full account of these factors and "cross sequential", a combination of cross sectional and longitudinal studies, have been proposed.3 It is clear that our understanding of the ageing brain continues to grow but still requires much research that is especially important given the numbers of elderly people in society and their potential levels of cognitive impairment. Where appropriate, randomised controlled trials of therapeutic measures may, in future, lead the way to greater understanding.

Abbreviations

AD - Alzheimer's disease

WML - white matter lesion

VaD - vascular dementia

Footnotes

Funding: none.

Conflicts of interest: none.

References

3. Raz N. The ageing brain: structural changes and their implications for cognitive ageing. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 2004115-134.

9. Levine B, Cabeza R, McIntosh A.[[ et al Functional reorganisation of memory after traumatic brain injury: a study with H ₂ ¹⁵O positron emission tomography. J Neurol Neurosurg Psychiatry 200273173-181. PubMed] PMC free article] [ Google Scholar]

11. Tullberg M, Fletcher E, DeCarli C.[[ et al White matter lesions impair frontal lobe function regardless of their location. Neurology 200463246-253. PubMed] PMC free article] [ Google Scholar]

13. Artero S, Tiemeier H, Prins N.[[ et al Neuroanatomical localisation and clinical correlates of white matter lesions in the elderly. J Neurol Neurosurg Psychiatry 2004751304-1308. PubMed] PMC free article] [ Google Scholar]

15. Hultsch D, Macdonald S. Intraindividual variability in performance as a theoretical window onto cognitive ageing. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 200465-88.

18. Parkin A.Memory and amnesia. Oxford: Blackwall, 1997

19. Reber A S.Dictionary of psychology. London: Penguin, 1995

20. Nyberg L, Bäckman L. Cognitive ageing: a view from brain imaging. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 2004135-160.

21. Cabeza R. Commentary: neuroscience frontiers of cognitive ageing: approaches to cognitive neuroscience of ageing. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 2004179-198.

27. Mukherjee J, Christian B, Dunigan K.[ et al Brain imageing of ¹⁸F‐Fallypride in normal volunteers: blood analysis, distribution, test‐retest studies, and preliminary assessment of sensitivity to ageing effects on dopamine D‐2/D‐3 receptors. Synapse 200246170-188. [ PubMed] Google Scholar]

30. Toescu E, Verkhratsky A, Landfield P. Ca[ ²⁺ regulation and gene expression in normal brain ageing. Trends Neurosci 200427614-620. [ PubMed] Google Scholar]

33. Herlitz A, Yonker J. Hormonal effects on cognition in adults. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 2004253-278.

35. Ng C, Panay N. Hormone replacement therapy update. Geriatric Medicine 20043427-34. [ Google Scholar]

59. Blauw G, Bollen E, Buchem M. et al Dementia at old age: a clinical end‐point of atherosclerotic disease. Eur Heart J 2001(suppl 3)N16-N19. [ PubMed]

75. Arneiz E, Almkvist O, Ivnik R.[[ et al Mild cognitive impairment: a cross‐national comparison. J Neurol Neurosurg Psychiatry 2003751275-1280. PubMed] PMC free article] [ Google Scholar]

80. Shepherd J, Blauw G, Murphy M, on behalf of the PROSPER study group et al Pravastatin in elderly individuals at risk of vascular disease (PROSPER): a randomised controlled trial. Lancet 20021-8. [ PubMed]

83. Sastre A, Grimley Evan J. Effect of the treatment of type II diabetes mellitus on the development of cognitive impairment and dementia. Cochrane Library. Issue 2. Oxford: Update Software, 2003

106. Hertzog C. Does longitudinal evidence confirm theories of cognitive ageing derived from cross‐sectional data? In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 200441-64.

Articles from Postgraduate Medical Journal are provided here courtesy of BMJ Publishing Group

# data[].attributes.attachment_link.description
Ageing causes changes to the brain size, vasculature, and cognition. The brain shrinks with increasing age and there are changes at all levels from molecules to morphology. Incidence of stroke, white matter lesions, and dementia also rise with age, as ...

# data[].attributes.headline
Chapter 1 Changes in Cognitive Function in Human Aging

# data[].attributes.subject
Chapter 1 Changes in Cognitive Function in Human Aging

# data[].attributes.attachment_link.readable_text
A. Attention

Attention is a basic but complex cognitive process that has multiple sub-processes specialized for different aspects of attentional processing. Some form of attention is involved in virtually all other cognitive domains, except when task performance has become habitual or automatic. Declines in attention can therefore have broad-reaching effects on one's ability to function adequately and efficiently in everyday life. The construct of attention defies simple definition, however, and it has been partitioned in a variety of ways by different researchers and theorists. The divisions used here are those that have been investigated most extensively in normal aging (for a comprehensive review of attention and aging, see [ 3]).

1. Selective Attention

Selective attention refers to the ability to attend to some stimuli while disregarding others that are irrelevant to the task at hand. For example, in visual search tasks, people are asked to search a visual display for a target letter that is surrounded by other nontarget letters. The task can be made more difficult by increasing the similarity of targets and distractors (e.g., search for an F in a background of Es), or by increasing the number of relevant or irrelevant features that are part of the search criteria. In another task - the Stroop task - people are asked to name the color of ink in which an incongruent color word is printed, (e.g., the word "red" printed in green). Here, the word information tends to interfere with color naming, causing errors and an increase in response times. To perform well in these kinds of tasks, people have to select the relevant stimulus or dimensions for processing and ignore the irrelevant ones. Although findings are not entirely consistent across studies and may differ across tasks, in general older adults appear to be slower than younger adults in responding to the targets, but are not differentially affected by distraction [ 3, 4]. Thus, deficits found in many of these tasks can be largely attributed to a general slowing of information processing in older adults rather than to selective attention deficits per se.

2. Divided Attention and Attention Switching

Divided attention has usually been associated with significant age-related declines in performance, particularly when tasks are complex. Divided attention tasks require the processing of two or more sources of information or the performance of two or more tasks at the same time. For example, people may have to monitor stimuli at two different spatial locations, or they may be asked to make semantic judgments about visually presented words while simultaneously monitoring for the occurrence of an auditorily presented digit [ 5]. The cost of dividing attention is assessed by comparing performance under dual task conditions to performance when the tasks are performed separately. Results suggest that older adults are more affected by the division of attention than young adults, particularly when the attentional demands of the two tasks are high. In addition, older adults seem less able to allocate resources appropriately when instructions are given to vary task priority [ 6]. These findings cannot be completely accounted for by a general slowing of information processing, but instead are usually explained in terms of declining processing resources associated with normal aging. Such limited resources are over-extended in older adults when attention must be divided between two or more sources. Similarly, the performance of older adults is slowed to a greater degree than that of young adults when attention must be switched from one task to another, requiring a change of mental set [ 4].

There is evidence that age deficits in divided attention and attention switching can be reduced by practice or extended training [ 7] and by aerobic exercise [ 8]. The exact mechanism of such improvements, however, is unclear. In the case of task-specific training, it is possible that some aspects of the tasks become automatic with practice, thus requiring fewer attentional resources. Alternatively, participants may develop strategies with extensive training that reduce the attentional demands of the tasks. It has been hypothesized that cardiovascular fitness may improve the efficiency of neural processes or may provide increased metabolic resources for task performance. Interestingly, the enhancement effects of aerobic exercise appear to be greatest on tasks involving executive control of attention [ 9], which depend largely on prefrontal cortex.

3. Sustained Attention

Sustained attention refers to the ability to maintain concentration on a task over an extended period of time. Typically, vigilance tasks are used to measure sustained attention, in which people must monitor the environment for a relatively infrequent signal, such as a blip on a radar screen. In general, older adults are not impaired on vigilance tasks.

4. Attention: Summary and Implications

Older adults show significant impairments on attentional tasks that require dividing or switching of attention among multiple inputs or tasks. They show relative preservation of performance on tasks that require selection of relevant stimuli; and although they are slower than young adults, they are not differentially impaired by distraction. They also are able to maintain concentration for an extended period of time. The tasks on which older adults show impairments tend to be those that require flexible control of attention, a cognitive function associated with the frontal lobes. Importantly, these types of tasks appear to be amenable to training and show benefits of cardiovascular fitness.

Attentional deficits can have a significant impact on an older person's ability to function adequately and independently in everyday life. One important aspect of daily functioning affected by attentional problems is driving, an activity that, for many older people, is essential to independence. Driving requires a constant switching of attention in response to environmental contingencies. Attention must be divided between driving, monitoring the environment, and sorting out relevant from irrelevant stimuli in a cluttered visual array. Research has shown that divided attention impairments are significantly associated with increased automobile accidents in older adults [ 3, 10]. Given the previously noted findings of the effects of practice, extended training on driving simulators under divided attention conditions may be an important remedial activity for older people.

B. Working Memory

Working memory is a multidimensional cognitive construct that has been hypothesized as the fundamental source of age-related deficits in a variety of cognitive tasks, including long-term memory, language, problem solving, and decision making. In fact, the majority of theories of cognitive aging seem to implicate working memory. Although there are several models of working memory, all agree that it is a limited capacity system that involves the active manipulation of information that is currently being maintained in focal attention (for reviews, see [ 11-13]). Short-term or primary memory, on the other hand, involves the simple maintenance of information over a short period of time. For example, one might maintain a phone number in short-term memory by simple rehearsal of the number. Older adults show minimal or no deficits in short-term memory and can typically hold about 7 ± 2 digits in mind as long as the digits are being rehearsed. Repeating the numbers backwards, however, requires an active reorganization or manipulation of the information held in short-term memory. This task thus requires working memory and shows impairments with age. In some sense, working memory is really a divided attention task - the contents of short-term memory must be maintained while simultaneously being manipulated or processed for some other purpose. Given the previously discussed findings of divided attention deficits with increased age, it is not surprising that older adults are impaired in working memory.

In the original working memory model of Baddeley and Hitch [ 14], the manipulation of information in short-term memory was handled by a central executive, and deficits in working memory were viewed as deficits in executive control, a function attributed primarily to prefrontal cortex. Recent neuroimaging research [ 15] has confirmed a role for dorsolateral prefrontal cortex (PFC) in the manipulation and updating of information in working memory, with left PFC involved more in verbal tasks and right PFC in visuospatial tasks. In recent years, however, the role of the central executive has been expanded to cover a range of executive control functions other than those associated strictly with working memory. These are elaborated in a later chapter section.

Although there is a general consensus that working memory is impaired in older adults, there is disagreement concerning the mechanisms involved, and much of the research has focused on testing a variety of theories. The next subsection outlines the main theories of working memory.

1. Theories of Working Memory

Three theories of cognitive aging have been articulated within the context of working memory deficits, although they may apply more broadly across other cognitive domains: (1) one theory proposes a reduction of attentional resources, (2) one focuses on reduced speed of information processing, and (3) one ascribes problems to a failure of inhibitory control (for review, see [ 16]).

a. Attentional Resources

Theories of age-related decline in working memory generally assume some reduction in processing resources. Craik and colleagues [ 17, 18] have suggested that the resource limitation is attentional and reflects a reduction in mental energy. Tasks with high attentional demands show impairments, whereas tasks requiring little or no attention (i.e., that are relatively automatic) are largely intact. Working memory tasks by their very nature involve divided attention and are therefore more likely to strain the limited resources of older adults. This theory is intuitively appealing, but it seems more descriptive than explanatory. The construct of attentional resources is poorly defined; and although neurophysiological correlates such as arousal or neural efficiency have been suggested [ 3], they have not been demonstrated empirically.

b. Speed of Information Processing

Salthouse [ 19] has suggested that speed of processing might be considered a resource, and that age-related deficits in working memory and other cognitive tasks can be explained in terms of a general slowing of information processing. There is little disagreement that older adults are slower than younger adults and that slowing of fundamental cognitive processes may have detrimental effects on more complex tasks. Debate has focused, instead, on whether a generalized slowing can account for the bulk of the empirical findings or whether more process-specific components are also needed. Salthouse [ 20, 21] has demonstrated in numerous studies that slowing of information processing can account for a large proportion of the age-related variance in a variety of cognitive tasks, including working and long-term memory, and has argued that speed of processing is a cognitive primitive. Other investigators [ 22], however, have suggested that speed of processing and working memory provide independent contributions to higher-level cognition, and that working memory deficits must therefore be accounted for in terms of something other than speed. Finally, at some level, slowed processing, like attentional resources, is more a descriptor of aging cognition than an explanation for cognitive deficits and says nothing about what causes slowing with age. Here too, therefore, discovery of neurophysiological correlates may help to clarify mechanisms.

c. Inhibitory Control

Hasher, Zacks, and May [ 23, 24] proposed that a lack of inhibitory control might account for cognitive deficits associated with aging. Specifically, failure to suppress irrelevant information in working memory may effectively reduce its capacity, denying access to relevant information. For example, working memory span tasks involve the successive presentation across trials of increasingly long strings of digits or words. Age deficits could be attributable to the failure to delete from working memory digits or words from prior trials, thus reducing the "working space" for new stimuli [ 25]. Although considerable data suggest that older adults experience more interference from irrelevant information under some conditions [ 26], findings are mixed and other data fail to support an inhibitory deficit account [ 3]. It may be that there are different kinds of inhibition or that age-related effects are task- or paradigm-specific.

2. Working Memory: Summary and Implications

Older adults exhibit significant deficits in tasks that involve active manipulation, reorganization, or integration of the contents of working memory. Although the mechanisms underlying these age-related deficits are as yet poorly understood, the effects of such deficits are very likely far-reaching. Many complex everyday tasks such as decision-making, problem-solving, and the planning of goal-directed behaviors require the integration and reorganization of information from a variety of sources. It seems likely that attention, speed of information processing, and the ability to inhibit irrelevant information are all important functions for effective performance of these higher-level cognitive tasks. Whether these functions might be subsumed under a domain-general executive controller that is impaired by normal aging -something akin to the central executive in Baddeley's model of working memory - or whether there may be multiple control processes that are independently affected by aging, is currently an issue under investigation. The brain regions that are active during working memory tasks are also beginning to be identified in a variety of functional neuroimaging studies. Results suggest that different areas are activated in young and old adults, particularly within the prefrontal cortex, indicating that younger and older adults are performing these tasks differently [ 12]. An understanding of age-related neurophysiological changes may help to account for these differences.

C. Long-Term Memory

The cognitive domain that has probably received the most attention in normal aging is memory (for reviews, see [ 13, 27]). Many older adults complain of increased memory lapses as they age, and a major focus of research has been to try to distinguish memory declines attributable to normal aging from those that are indicative of pathological aging, particularly Alzheimer's disease. Like attention, memory is not a unitary construct; some kinds of memory remain relatively intact with age while others show significant declines. Long-term memory, unlike short-term and working memory, requires retrieval of information that is no longer present or being maintained in an active state. This information could have occurred a few minutes ago or been acquired many years ago. The next subsections review age-related changes in various kinds of long-term memory.

1. Episodic Memory

Episodic memory refers to memory for personally experienced events that occurred in a particular place and at a particular time. This kind of memory allows one to think back through subjective time - what Tulving calls mental time travel [ 28] -and it usually evokes an "I remember" response. Episodic memory may be distinctly human; it is the most advanced form of memory and is ontogenetically the latest to develop. It also seems the most susceptible to brain damage and the most affected by normal aging.

The episodic memory problems experienced by older adults may involve deficient encoding, storage, or retrieval processes. At the input stage, older adults may encode new information less meaningfully or with less elaboration, so that memory traces are less distinctive, more similar to others in the memory system, and thereby more difficult to retrieve [ 29]. Alternatively, older people may attend to focal or salient information but fail to take account of peripheral detail, or they may fail to integrate contextual aspects of an experience with central content - what is sometimes referred to as a source memory problem [ 30]. Many of the common everyday memory lapses reported by normal older adults, such as forgetting where they parked their cars, likely involve poor encoding. These kinds of memory failures have generally been attributed to reduced use of effortful encoding strategies, which depend particularly on prefrontal brain regions. Another possibility is that noticing and integrating the various aspects of an experience involve divided attention and require working memory.

Older adults may also experience problems at the level of storage or consolidation. This aspect of episodic memory critically depends on medial temporal lobe structures, particularly the hippocampus. Consolidation is thought to involve the binding of various aspects of experience into a composite memory trace. What may be particularly critical for episodic memory and impaired in older adults is the extent to which an event is bound to its spatial and temporal context.

Finally, considerable evidence points to retrieval as a source of episodic memory problems in aging. Although it is clear that retrieval is at least partly dependent on encoding (i.e., well-encoded information is easier to retrieve), there are also effortful retrieval processes that appear to be impaired by aging. Older adults tend to show deficits on tests of free recall, to a somewhat lesser degree in cued recall, but minimally in recognition memory. Craik [ 18] has argued that the requirement to self-initiate strategic search processes in recall taxes the limited resources of older people. To the extent that environmental support can be provided at retrieval as well as at encoding (by providing good cues or using recognition tests, for example), the resource demands of encoding and retrieval are reduced and age differences are minimal. Similarly, Jennings and Jacoby [ 31] have demonstrated that recollection, which requires effortful retrieval of episodic detail, is impaired with age, whereas the more automatic judgments of familiarity are intact. Evidence from functional neuroimaging and neuropsychological studies suggests that these more strategic retrieval processes depend on the prefrontal cortex, as well as the hippocampus [ 32, 33].

2. Semantic Memory

Semantic memory refers to one's store of general knowledge about the world, including factual information such as "George Washington was the first president of the United States" and knowledge of words and concepts. Such information is not tied to the space or time of learning, and its retrieval is generally prefaced with "I know." Normally aging older adults do not have significant impairments in semantic memory. In fact, their knowledge of the world often exceeds that of young people. In addition, although access to information may be somewhat slower (particularly for words and names), the organization of the knowledge system seems unchanged with age (for review, see [ 34]). Semantic memories are believed to be stored in a variety of regions in posterior neocortex.

3. Autobiographical Memory

Autobiographical memory involves memory for one's personal past and includes memories that are both episodic and semantic in nature. The bulk of the evidence suggests that recent memories are easiest to retrieve, those from early childhood are most difficult to retrieve, and there is a monotonic decrease in retention from the present to the most remote past, with one exception. Events that occurred between the ages of 15 and 25 are recalled at a higher rate - what is referred to as the reminiscence bump - a finding that has usually been attributed to the greater salience or emotionality of the memories during this time period. This general pattern holds across all ages, suggesting that autobiographical memory is largely preserved with age (for review, see [ 35]). More detailed analyses of the nature of the autobiographical information retrieved, however, has suggested that although memory for personal semantics is intact in old age, memory for specific episodic or contextual details about one's personal past may be impaired. In a recent study, Levine et al. [ 36] observed that although older adults reported the gist of autobiographical event memories as well as young people, they reported fewer details. There may be exceptions to this finding, however. Recent studies of flashbulb memory have demonstrated that older adults remember as much as young adults about the details and circumstances surrounding highly emotional public events such as the death of Princess Diana or the 9/11 attack on the World Trade Center in New York City [ 37, 38].

4. Procedural Memory

Procedural memory refers to knowledge of skills and procedures such as riding a bicycle, playing the piano, or reading a book. These highly skilled activities are acquired more slowly than episodic memories through extensive practice. Once acquired, procedural memories are expressed rather automatically in performance and are not amenable to description (i.e., it is not easy to say "how" one reads). When talking about procedural memory or knowledge, one is likely to say, "I know how to." In general, older adults show normal acquisition of procedural skills in both motor and cognitive domains and retain them across the lifespan. With high levels of expertise, there is often little slowing of skilled performance with age (at least until the very oldest ages), although some individual components of the skill may decline. So, for example, although the finger movements of a skilled typist slow down with age, overall typing speed is maintained because other aspects of the skill adjust (e.g., scanning further ahead in the text to be typed) [ 39]. Procedural memory depends on several brain regions, including the basal ganglia and the cerebellum.

5. Implicit Memory

Implicit memory refers to a change in behavior that occurs as a result of prior experience, although one has no conscious or explicit recollection of that prior experience. For example, laboratory experiments have shown that it is easier to identify a degraded stimulus (e.g., from a brief exposure or partial information) if the stimulus was seen previously, even if one does not remember the prior occurrence. This "priming" probably occurs ubiquitously in everyday life and appears relatively intact in normal aging, although there are some inconsistencies in the literature (for review, see [ 40]). The most extensively studied form of implicit memory is perceptual priming, which occurs in response to a perceptual cue. Perceptual priming is modality specific and depends on sensory processing areas of the brain (e.g., in the visual domain, priming involves extra-striate regions of the visual cortex). Conceptual priming, which requires semantic processing and is observed in response to a conceptual cue, is also preserved in many older adults, and has been associated with left frontal and left temporal cortical regions.

6. Prospective Memory

Much of what we have to remember in everyday life involves prospective memory - remembering to do things in the future, such as keep appointments, return a book to the library, or pay bills on time (for review, see [ 41]). Older adults do quite well on these daily tasks, using a variety of external aids such as calendars and appointment books to remind themselves of these activities. Certain habitual tasks such as taking medications at the appropriate times each day, however, may create difficulties for older people. For these tasks, there often are no salient reminders or cues in the environment, and so the tasks require the kinds of self-initiated activities that seem to be particularly problematic for older adults. Prospective memory may also rely on some aspect of working memory to maintain future intentions over time and likely also involves divided attention, both functions that show age-related deficits. Prospective memory and episodic memory tend not to be correlated and probably depend on different regions of the prefrontal cortex.

7. Long-Term Memory: Summary and Implications

Aging principally affects episodic memory, namely memory for specific events or experiences that occurred in the past. Although many older adults believe that their memories for remote events are better than their memories for recent events, it is likely that older memories have become more semantic or gistlike, retaining the general core information but lacking details, particularly spatial and temporal context. These older memories have often joined the realm of things that we now "know." More problematic for older adults is remembering context or source information: where or when something was heard or read, or even whether something actually happened or was just thought about, what has been called "reality monitoring" [ 42]. Encoding and retrieval of these kinds of specific or peripheral details about a prior event may be particularly demanding of attentional resources, and good cues for the retrieval of such information may often be lacking. Although semantic memory is largely preserved in old age, the fact that what is retrieved from semantic memory is general knowledge, not specific detail, may contribute to the absence of age differences. The exception to this pattern might be the retrieval of a person's name or a specific word for a specific context, both of which show deficits in normal aging. The specificity of the information to be retrieved may therefore be a critical determinant of age differences [ 43]. There is some suggestion that age-related deficits in memory may be reduced for emotionally arousing events or materials [ 38], and so emotional or personal investment in an experience may be an important variable in episodic memory in older adults. High levels of emotion or stress, however, generally have negative effects on memory.

D. Perception

Most people view perception as a set of processes that occurs prior to cognition. However, the boundaries between perception and cognition are unclear, and much evidence suggests that these domains are interactive with top-down cognitive processes affecting perception and perceptual processing having a clear impact on cognition. Evidence indicates that perceptual function is reduced in most older adults and is not always correctable by external aids (for review, see [ 44]). This suggests, at the very least, that researchers should pay careful attention to and control for sensory and perceptual deficits when conducting cognitive experiments. Evidence from a range of large-scale aging studies has demonstrated that a significant proportion of the age-related variance in several cognitive tasks can be accounted for by hearing and vision loss and that once these sensory differences are statistically controlled, there are no longer age differences in cognitive functioning [ 45]. Baltes and Lindenberger [ 45] proposed that overall neural degeneration may account for both sensory and cognitive deficits - what has been called the common cause hypothesis. Alternative explanations have also been proposed, however. For example, Schneider and Pichora-Fuller [ 44] suggested that perception and cognition are part of a highly integrated system and draw on a common pool of attentional resources. When parts of this system are stressed, such as when auditory or visual acuity are compromised and are essential to a task, other parts of the system will be negatively affected.

Declining sensory and perceptual abilities have important implications for the everyday lives of older adults. Hearing loss can isolate older people, preventing them from engaging in conversation and other social interactions. Visual impairments can limit mobility and interact with attentional deficits to make driving a particularly hazardous activity. As older people develop strategies to compensate for declining sensory abilities, the ways in which they perform other cognitive tasks may also be altered and may be less efficient. Retraining and practice on these tasks may help the adjustment and improve performance.

A. Speech and Language

Speech and language processing are largely intact in older adults under normal conditions, although processing time may be somewhat slower than in young adults. In fact, there is evidence that discourse skills actually improve with age. Older people often tell well-structured elaborate narratives that are judged by others to be more interesting than those told by young [ 46]. They usually have more extensive vocabularies; and although they exhibit the occasional word-finding difficulty, older adults are easily able to provide circumlocutions to mask the problem. They are skilled conversationalists and appear to have few difficulties in processing ongoing speech. As noted above, however, some older adults have hearing loss and so, in conversational settings, may be required to interpret a weak or distorted acoustic signal. Even under these conditions, older people seem able to maintain good levels of comprehension by effectively using context to interpret the message [ 47]. Nevertheless, this compensatory top-down processing may have negative consequences for other cognitive operations and may be at least partly responsible for reducing the functional capacity of working memory. The converse relation has also been proposed, however, namely that the well-documented reduced working memory capacity in older adults limits the comprehension of syntactically complex text. The fact that comprehension of text is often measured by recall, a cognitive function known to be impaired in aging, complicates still further the interpretation of comprehension deficits. Older adults also experience problems with comprehension when individual words are presented at a very rapid rate, but they show sharply reduced impairments when such words form meaningful sentences. Here also, older people seem able to engage intact top-down processes to bolster deficiencies in bottom-up processing. They thus appear to retain good language skills well into older age. Deficits that occur under difficult processing conditions seem primarily attributable to sensory loss or working memory limitations, not to impairments in basic language capacities per se (for a comprehensive review, see [ 48]).

B. Decision Making

Relatively little research has been done on the effects of aging on decision-making. Most of the work has highlighted the potential impact of attentional and working memory limitations on the ability to make decisions, but also has incorporated ideas involving motivation, relevance, emotional investment, and prior knowledge as important moderators of those effects, particularly in real-life contexts. Decision-making seems to be a domain that makes clear demands on processing resources, but in everyday life those demands may be reduced by life-relevant knowledge or expertise in the problem-solving domain. For example, research has shown that when making decisions about healthcare alternatives, buying a car, or buying insurance, older adults often come to the same kinds of decisions as younger adults but reach their conclusions in a different way. They tend to rely more on prior knowledge about the problem domain and less on new information, whereas young people, who likely have less knowledge about these issues, tend to sample and evaluate more current information and consider more alternatives before making their decisions (for review, see [ 49]).

Older adults, again possibly because of working memory limitations, tend to rely on expert opinion to a greater degree than young adults. Although this strategy may work reasonably well when the expert is well-qualified (e.g., a physician for medical decisions), it may leave older people susceptible to things such as investment scams. Poor decision-making may also be a result of episodic memory decline, particularly the loss of memory for details or source. For example, remembering that "Stock ABC is a good investment," without remembering where one heard such information, could lead to a bad decision.

C. Executive Control

In the past decade, there has been an increasing focus on executive control as a primary contributor to cognitive decline with age. Executive control is a multi-component construct that consists of a range of different processes that are involved in the planning, organization, coordination, implementation, and evaluation of many of our nonroutine activities. This so-called central executive [ 14, 50] plays a key role in virtually all aspects of cognition, allocating attentional resources among stimuli or tasks, inhibiting distracting or irrelevant information in working memory, formulating strategies for encoding and retrieval, and directing all manner of problem-solving, decision-making, and other goal-directed activities. Executive control is particularly important for novel tasks for which a set of habitual processes is not readily available. Executive function depends critically on prefrontal cortex, which exerts its broad-reaching controlling influence via extensive reciprocal connections with posterior cortical regions. A parsimonious explanation of cognitive aging ascribes a causal role to executive control deficits - what has been called the frontal lobe hypothesis of aging [ 51]. In support of this hypothesis, both structural and functional neuroimaging studies have revealed a preferential decline in older adults in volume and function of prefrontal brain regions [ 52].

# data[].attributes.attachment_link.title
Changes in Cognitive Function in Human Aging

# data[].attributes.attachment_link.description
As people age, they change in a myriad of ways - both biological and psychological. Some of these changes may be for the better, and others are not. This book primarily concerns the normally aging brain, the neuroanatomical and neurophysiological changes that occur with age, and the mechanisms that account for them.

# data[].attributes.headline
Microstructural maturation of the human brain from childhood to adulthood

# data[].attributes.subject
Microstructural maturation of the human brain from childhood to adulthood

# data[].attributes.attachment_link.readable_text
To access the Library, GCU students and faculty must login. The username and password is the same as your GCU login.

Before accessing the databases, please review Grand Canyon University's Copyright Notice and Terms of Use

Please Log In

Need Help?

If you have forgotten your password or are having trouble logging in, please click here to reset your password. If the login issue persists, please contact Technical Support at Toll Free: 877.428.8447 or Local: 602.639.7200 or visit their web page for live chat.

# data[].attributes.attachment_link.description
To access the Library, GCU students and faculty must login. The username and password is the same as your GCU login. Before accessing the databases, please review Grand Canyon University's Copyright Notice and Terms of Use If you have forgotten your password or are having trouble logging in, please click here to reset your password.

# data[].attributes.attachment_link.readable_text
To access the Library, GCU students and faculty must login. The username and password is the same as your GCU login.

Before accessing the databases, please review Grand Canyon University's Copyright Notice and Terms of Use

Please Log In

Need Help?

If you have forgotten your password or are having trouble logging in, please click here to reset your password. If the login issue persists, please contact Technical Support at Toll Free: 877.428.8447 or Local: 602.639.7200 or visit their web page for live chat.

# data[].attributes.attachment_link.description
To access the Library, GCU students and faculty must login. The username and password is the same as your GCU login. Before accessing the databases, please review Grand Canyon University's Copyright Notice and Terms of Use If you have forgotten your password or are having trouble logging in, please click here to reset your password.

# data[].attributes.headline
Cognitive Development in Middle Adulthood

# data[].attributes.subject
Cognitive Development in Middle Adulthood

# data[].attributes.attachment_link.readable_text
Loading...

Cognitive Development in Middle Adulthood

Section Introduction

Learning Objectives

Identify and define terms, theories, and concepts during the middle adulthood stage of cognitive development

Previous Next

Stress in Middle Adulthood

Intelligence in Middle Adulthood

# data[].attributes.attachment_link.title
Cognitive Development in Middle Adulthood - Liberty University - Course Apps

# data[].attributes.attachment_link.description
Section 2 Introduction - Adults in middle age witness continued cognitive development, with many individuals becoming experts in a particular area of study or occupation. Though the brain has already reached maturity, the demands of life produce both cognitive gains and losses in this stage of development.

# data[].attributes.headline
Emerging Adulthood as a Critical Stage in the Life Course

# data[].attributes.subject
Emerging Adulthood as a Critical Stage in the Life Course

# data[].attributes.attachment_link.readable_text
David Wood

Tara Crapnell

Lynette Lau

Ashley Bennett

Debra Lotstein

Maria Ferris

Alice Kuo

1 Introduction to Emerging Adulthood

The path that individuals take from dependency in childhood to independence in adulthood is now a longer and more complicated one than at any other point in history (Arnett ). From the mid- to late twentieth century and extending into the twenty-first century, industrial societies have experienced a surge in the concept of individualism and increased salience of self-realization and personal expression (Arnett ). Moreover, we have seen a dramatic increase in the number of youth seeking post-high school education, which is required for success as the economy transitions from an industrial to an information-based economy (Rifkin ). However, stagnation of wages for low-skilled workers and the lack of work opportunities for youth and young adults, combined with the increased costs of education and independent living, have made the pathway to independence and adulthood prolonged, complex, and varied, creating a new stage in the life course that has been labeled emerging adulthood (EA). While not all life course or developmental scientists agree that emerging adulthood constitutes a new developmental stage, there is agreement that social and economic forces have prolonged entry into adulthood and with significant role and developmental challenges beyond the traditional adolescent years (Cote ).

At the beginning of this stage, 17-18 years of age, emerging adults are generally dependent, living with their parents or caretakers, beginning to engage in romantic relationships, and attending high school. At the end of this stage, mid- to late 20s, most emerging adults live independently, are in long-term relationships, and have clear career paths ahead of them. How they traverse this life stage is dependent upon the personal, family, and social resources they possess as they enter this stage of life, dynamic and reciprocal interaction between the emerging adult and their environment, and the supports they receive during this stage. The result is that there are many pathways that youth and young adults pursue through this stage to achieve stable adulthood. For example, 40% do not pursue post-high school education. While 60% entered college immediately after graduating high school, many drop out or interrupt their college education with periods of work. Some 33% in this stage remain unmarried; however, 67% of them achieve stable domestic partners. Importantly, only a minority of emerging adults are employed in full-time jobs, limiting the economic opportunities they experience (U.S. Census Bureau. American Community Survey ).

Emerging adulthood is considered to be the volitional years , as it offers the most opportunity for identity exploration in the areas of love, work, and worldviews (Arnett ). During this time, individuals begin to develop the characteristic qualities necessary for becoming self-sufficient, engage in mature, committed relationships, assume more adult roles and responsibilities, and obtain a level of education and training that sets the foundation for work during the adult years. Characterizing emerging adulthood as a stage in the life course has proven to be beneficial to explain the social, cognitive, and psychological development that occurs during this stage. Research demonstrating continued brain development into the late 20s provides further justification for viewing emerging adulthood as a stage in the life course (Spear ).

2 Conceptual Framework

The Life Course Health Development (LCHD) model posits that myriad factors (e.g., biological, psychological, cultural) on multiple levels (e.g., micro, meso, macro) interact simultaneously in a transactional fashion to influence an individual's LCHD during each stage to determine a "health developmental" trajectory (see also Halfon and Forrest ). The Life Course Health Development (LCHD) model further posits that transitions and pivotal points in an individual's life have the potential to influence and alter an individual's developmental pathways. EA is a life stage characterized by changes in person-context cognitive, emotional, physical, and social domains, and the ultimate pathway achieved by the emerging adults during this stage is determined by the ongoing, dynamic, and reciprocal interactions between the individual and their environment. The degree of agency and role exploration that characterizes EA results in the potential for growth in intellectual and emotional functioning (Arnett ). EA represents a broad and diverse but fundamentally important area of consideration by virtue of the multiple avenues through which an individual's developmental trajectories and outcomes may be influenced. Important developmental challenges during EA include the continued formation of identity and values, which occur in the midst of frequent changes in personal relationships, living arrangements, vocational and educational pursuits, and social roles (Shanahan ).

No stage in life, other than perhaps infancy, experiences such dynamic and complex changes on the personal, social, emotional, neuroanatomical, and developmental levels. For the 10 years between 18 and 28, the vast majority of emerging adults change living situation, change their primary relationships, complete education or vocational preparation, get married, have children, and transition from adolescent/dependent roles to adult/independent roles. This occurs during often volatile emotional, neurodevelopmental, and social development. Increasing agency occurs at the same time as decreasing institutional and family supports. The theoretical framework developed by Learner and others to create the positive youth development theory nicely explains how the developmental trajectories that emerge during the period of EA are dependent upon multiple influential, bidirectional, person-context coactions. Individuals during emerging adulthood act as co-developers of their own developmental pathways, adaptively responding to different biological, social, cultural, and physical environmental contexts that they influence and are also influenced by (Learner and Overton 2008). Successfully navigating the developmental challenges inherent in EA will likely, in large part, influence the developmental trajectory of adulthood because these challenges ultimately influence the important adult outcomes of independent living, committed intimate relationships, and vocational and educational achievement. Youth and young adults with chronic disease or disabilities face additional challenges (disease management, disease complications, limitations in opportunities, etc.) in the context of these multiple domains of growth and development, which impact their pathway through this stage.

The continued positive trajectory of the emerging adult's mental health, identity formation, education achievement, social relationships, and other developmental areas is somewhat dependent on the degree to which there are matches or mismatches between the individual and his/her resources and the environmental challenges and supports. If the transition, such as school to work, provides a reasonable and developmentally appropriate challenge and the emerging adult successfully navigates that challenge, then the developmental trajectory of the emerging adult will be enhanced. In contrast, if the same transition lacks supports or is an inappropriate match for the emerging adult's abilities (e.g., an inadequate vocational program for an emerging adult with a learning disorder or lack of support for chronic disease management) and the emerging adult experiences failure, then the developmental trajectory may be impaired, resulting in significantly less achievement or developmental progression across the lifespan. A major defining characteristic of the stage of EA is that contexts are changing significantly (family to independence or romantic relationships, school to work or disconnected state, dependent living to independent living arrangements). The changes are so significant that emerging adults need substantial supports to navigate the transition successfully. Emerging adults with disabilities or chronic health conditions require more support to maximize their potential development during EA (Table ).

The above table outlines the seven principles of the Life Course Health Development framework. These principles can be applied to the stage of emerging adulthood in a limited fashion due to the limited research literature focused on this life stage. However, conceptually, using the seven principles to view the stage of emerging adulthood can be instructive and can lead to additional research questions (see end of this article). For example, Principle 5 states that health development expressions are malleable and enable and constrain health development pathways and plasticity. According to Bogin's reserve capacity hypothesis, prolonged childhood into adolescence and perhaps emerging adulthood leads to greater biologic and social resilience in adulthood, which leads to enhanced fertility and greater longevity (Bogin ). Principle 4 states that health development is sensitive to life course timing and social structuring of the environment. As we described above, this is particularly true of emerging adulthood, where the interaction between age, personal development, and environment (peers, schools, social institutions, etc.) leads to multiple pathways to identify formation and academic and social achievement during this stage (Benson and Elder ; Benson et al. ).

Multiple factors can influence the life course during EA, including factors at the macro-level (historical and societal influences), meso-level (parent-child relationship, family environment, and socioeconomic status), and microlevel (individual cognitive, personality, and emotional development). The timing of these exposures during EA, which we consider a critical or sensitive period in the life course development, can significantly impact adult outcomes. For example, an emerging adult that engages in criminal activity and is convicted of a felony will suffer repercussions that will greatly diminish their chances of achieving success in relationships and work. In the sections that follow, we review the macro-, meso-, and microlevel influences occurring during EA for emerging adults generally. Next we explore the additional challenges faced by those with selected chronic health or developmental conditions including mental illness or substance abuse, diabetes, chronic renal failure, and autism, to serve as case studies of the increased complexity faced by emerging adults with chronic disease. Finally, we finish up with a set of questions and issues that are research priorities for developing an LCHD research agenda on the stage of emerging adulthood.

3 Macro-level Influences on the Trajectory of Emerging Adulthood

Emerging adulthood, like many other developmental stages, is a period in the life course that is culturally constructed and not universal (Arnett , ). Thus, the very existence and trajectory of EA are dependent on macro-level societal expectations and influences. For many years, it was theorized that an individual transitioned from adolescence (which begins in puberty and ends in the late teens) into young adulthood. Over history and cross-culturally, the length of time during which an individual spends in adolescence has been determined by the age at which the person enters marriage or a committed relationship (Schlegel and Barry III , Gilmore ). In fact, human life history posits that the life stage of adolescence came into existence about 75,000 years ago due to changes in human societies and cultures associated with pair bonding and living in large groups (Bogin ). So massive culture and reproductive change led to a change in life history with the addition of a new period of development. It is theorized by those promoting emerging adulthood as a new life stage that the same kind of massive cultural and reproductive change is happening once again and new social and cultural demands of adult life necessitate a longer and more complex prologue to adult life.

Although the functional outcome of EA, causing a delayed transition to adulthood, appears relatively novel, this practice of prolonging the transition to adulthood may be dated back to early modern English society from the 1500s to 1700s (Ben-Amos ). Similar to what generally occurs during EA today, individuals during that era took part in a "life cycle service " between their late teens and 20s, wherein they would engage in developing important vocational skills (e.g., a trade or craft) and marriage was often postponed until the late 20s for both men and women; adult roles and responsibilities for individuals during that era were provided only gradually, as each individual acquired the desired character qualities deemed appropriate by society (Ben-Amos ). It was not until industrialization in America began to emerge in the nineteenth century that the concept of individualism developed and strengthened (Rotundo ). The twentieth century marked the first time that an individual could obtain and gain control over the resources that would allow them to choose the timing of major life events and personal expression was valued in society (Modell ).

As we move forward into the twenty-first century, individualism in contemporary postindustrial society continues to strengthen, while the age at which individuals marry continues to increase, and individuals increasingly seek to pursue other life course events (Modell ; Alwin ; Bellah et al. ). As a reflection of these trends, recent evidence indicates that contemporary postindustrial society considers marriage status of low importance in the determination of whether or not an individual has reached adulthood; rather, societies in developed countries appear to now consider the acquisition of certain character qualities as the most important indicator of having attained adulthood, the top three character qualities of which include (1) accepting responsibility for oneself, (2) making independent decisions, and (3) assuming financial independence - all of which emphasize an individual's ability to be self-sufficient (Scheer et al. ; Greene et al. ; Arnett , ).

4 Meso-level Influences of Life Trajectories During Emerging Adulthood

Earlier life experiences and family environment can impact one's life trajectory from childhood through EA and into adulthood. Longitudinal studies that span early childhood through EA indicate that there is both continuity and discontinuity of healthy and unhealthy paths and outcomes. (Masten et al. , ). In this section, we will be discussing the impact of the parent-child relationship, family environment, and other sociodemographic factors, such as socioeconomic status (SES) and its influence in EA.

4.1 Earlier Parent-Child Relationships

4.2 Childhood Socioeconomic Status

Socioeconomic status (SES), family supports, and the neighborhood environment all can contribute to the positive or negative life trajectory prior to and during EA (Galobardes et al. ; Gilman ; Gilman and Loucks ). Socioeconomic status has been identified as one of the most important health determinants throughout the life course (Miller et al. ). Low financial resources and all the other exposures that go along with poverty - poor schools, chaotic families, exposure to violence, and victimization - limit opportunities for growth or acquisition of other resources that enhance quality of life (Wadsworth et al. ; Kim et al. ).

However, while SES has been found to be predictive of educational attainment, the impact of poverty can be mitigated by a number of factors such as individual characteristics of self-efficacy and hope. Students from poor families that have high self-efficacy and a similar concept of hope for educational attainment do equally as well in school as their higher SES peers (Osgood et al. ). Recent research by Dweck and colleagues indicates that students' mindsets are critically linked to resilience and achievement and that they can be changed through brief interventions, leading to substantial increases in measures of resilience and achievement (Yeager and Dweck ). These studies suggest that in addition to SES, individual characteristics also have a large influence on outcomes of EA and that these characteristics can be influenced through individual interventions. Individual characteristics and development are discussed in the next section.

5 Microlevel Influences on the Trajectories During Emerging Adulthood

As discussed in previous sections, individualism and the qualities of character have become increasingly important in the transition to EA and ultimately reaching full adulthood in postindustrial, developed societies. Studies have shown that the ability to accept responsibility for one's self, make independent decisions, and assume financial independence are the top three most important factors in becoming an adult (Arnett ). In order to achieve individualism and obtain these important qualities of character, one needs to reach some degree of cognitive and psychological maturity, as well as possess some level of resilience. These individual factors are discussed in this section.

5.1 Cognitive Development

One of the identified qualities of character that is important in EA and reaching full adulthood is independent decision-making. While the ability to make independent decisions is a reflection of one's psychological and moral identity, it also has to do with cognitive maturity and the ability to weigh a variety of considerations before deciding on a choice. Recent neuroscience research indicates that brain development (particularly in the prefrontal cortex) continues well into the third decade of life, ultimately resulting in the integration and coordination of cognitions, emotion and action, and strategic executive control (Luciana et al. ). The continuous unfolding and acquisition of specific neurodevelopmental capacities during adolescences and EA influence the acquisition of goal directedness and future orientation that have been observed behaviorally during EA (Dahl ; Nelson et al. ; Nurmi ; Steinberg et al. ). As new capacities emerge, they are available to solve problems, delay gratification, and filter unnecessary input. With maturation of these skills, emerging adults are also more capable of reflecting on the influence of their environment and on their internal state, regulate their emotions, and use problem-solving skills to effectively compromise, which is important for the development of meaningful social interactions and personal relationships as well as in the work environment. These skills also support an emerging adult's capacity for optimally interacting with the health-care system, managing their health-care needs, and making decisions that will influence their long-term health outcomes.

However, the preceding paragraph assumes that the individual has experienced optimal neurodevelopment up to the point that they enter the stage of EA. Studies have demonstrated that exposure to chronic stress during childhood (e.g., poverty) or experiencing adverse childhood events (e.g., child maltreatment, neglect, parental divorce, parental substance abuse) may cause detrimental impact to the developing brain. For example, repeated exposure to stressful events has been associated with structural differences in specific brain regions (i.e., amygdala, hippocampus, and prefrontal cortex), which are in turn associated with functional differences in learning, memory, and aspects of executive functioning. Furthermore, preliminary studies go on to suggest that there may be sensitive periods of brain development with increased susceptibility to the effects of stress and adverse events. These environmentally induced modulations in neurodevelopment can impact an individual's cognitive development and their capacity to develop the necessary skills and relationships that will enable them to thrive.

An emerging adult, who has experienced chronic stress or adverse events earlier in childhood and adolescence and is cognitively immature, is more likely, through adverse interaction with their environment, to suffer secondary effects such as school failure, risky/impulsive behaviors, accidental injury, criminal activity, or substance misuse or overuse. These behaviors may in turn interfere with the ongoing development of an optimal pathway to adulthood. Feelings of isolation and rates of substance abuse in individuals often peak during this period as emerging adults are faced with the stresses of having to navigate societal structures that are not adequately informed or equipped to address the needs of an emerging adult population - all while their brains have yet to reach full maturation (Spear ). An impulsive emerging adult fueled by alcohol and despair is at high risk for suicide. It is thus apparent that multiple factors related to an individual's cognitive and emotional development may intersect and interact to multiply the likelihood of adverse or positive health outcomes in EA. It is crucial for service providers to recognize the level of cognitive maturation an emerging adult possesses and tailor their interventions and supports based on this.

5.2 Identity Formation

Identity formation is a major developmental activity during EA. Identity development, occurs in a number of dimensions: (1) psychological dimension, or ego identity via a sense of temporal-spatial continuity and its concomitants; (2) the personal dimension, or a behavioral and character repertoire that differentiates the individuals; and (3) the social dimension, or recognized roles within a community. These components come together during the stage of identity formation (adolescence and EA) and stabilization (EA and young adulthood), and once the identity is considered stable, this is when a relatively firm sense of ego identity is developed, behavior and character become stabilized, and community-sanctioned roles are acquired (2002).

Identity formation during adolescence was thought to be a critical milestone in adolescence; however, it has been recognized that in certain societal contexts, identity formation continues beyond adolescence. In the postindustrial society, with the prolongation of educational and vocational attainment, prolongation of identity exploration in the three main areas of love, work, and worldviews into the 20s has become the norm. Identity formation is critical in EA, as it has direct implications on psychological and moral identity and in achieving the three qualities of character deemed as important in the transition to adulthood.

5.3 Resilience in Emerging Adulthood

Resilience is an individual's capacity to adapt to change in healthy and flexible ways during stressful events (Catalano et al. ). Resilience can be measured in various ways, including internal adaption (e.g., well-being, happiness, or self-concept) or external adaption (academic achievement, relationship development) to adverse circumstances, such as how well a person navigates and achieves the developmental tasks presented by the external world (e.g., educational achievement, stable work/career, marriage, etc.). Resiliency in adolescence and young adulthood is higher among youth with higher intellectual resources, optimistic future orientation, the presence of caring relationships with positive adult role models, and opportunities to succeed and serve the community. Emerging adulthood is a particularly important stage in the life course to understand resilience because the important changes in functional capacity, educational achievement, and social roles are large and varied and have a significant influence on life course outcomes.

Key individual characteristics that predict resilience during EA are goal-directed motivation and planfulness about the future. In addition, adult support and mentorship are important factors that help promote resilience (Miller GE ; Masten et al. ; Arnett ). Furstenberg, Brooks-Gunn, and others studied young women who became pregnant during adolescence and found that a small proportion with positive adult relationships had dramatic change in trajectory for the better (Furstenberg ). Masten, studying a cohort of low-income youth (beginning at ages 8-12) over a 20-year period, found that a number of factors predict competence in EA including higher intellectual capacity, higher parenting quality, and higher SES (Masten and Coatsworth ). When they examined resilience between the 10- and 20-year follow-up, they found that youth doing well in EA was predicted from doing well 10 years earlier. In the context of high adversity, childhood IQ was particularly an important moderator and predictor of resilience. During EA, individuals who were doing well from high-adversity backgrounds had significant personal resources in intelligence and personal competence and a history of receiving high-quality parenting (Masten et al. ).

6 Trajectories During Emerging Adulthood for Emerging Adults with Chronic Health Condition

Chronic health conditions can significantly impact the developmental trajectory of emerging adults during this life stage. Many types of chronic conditions, including those that impact physical, intellectual, or emotional functioning, may undermine the assumption of adult roles by the emerging adult, undermine success in school, impair the transition to work, and make living independently more of a challenge. Eighteen percent of youth aged 12-17 in the USA are defined as having a special health-care need , meaning they have a chronic physical, medical, emotional, or developmental condition that requires a more intensive use of health-care and related services. Emerging adults with chronic conditions are at risk for a number of problems during transition to adulthood, including experiencing gaps in needed medical and related services and gaps in health insurance (Lotstein et al. , Reiss et al. ). Below we review the impact of several specific chronic conditions on the growth trajectory during emerging adulthood.

6.1 Autism Spectrum Disorders (ASDs)

For youth with autism spectrum disorders (ASDs) and their families, the transition from adolescence to emerging adulthood is a time of uncertainty and loss of entitlement to many services that were available while in the public school system under the Individuals with Disabilities Education Act (IDEA). In comparison to childhood, young adults with autism often experience a dearth of appropriate supports and opportunities. Leaving high school is associated with deterioration in ASD symptom presentation, increase in maladaptive behaviors, and worsening family functioning (Taylor and Seltzer , , ). Many persons with ASD are able to work successfully within the community (Garcia-Villamisar et al. ; Mawhood and Howlin ); however, the majority experience difficulty securing meaningful employment (Eaves and Ho ; Howlin et al. ; Newman et al. ). A recent study indicated that only 58% have ever worked for pay. In addition, it was found that only one in five individuals ever lived independently (Roux et al. ). Even among those employed, their jobs tended to be low level and low income (Cimera and Cowan ; Eaves and Ho ; Howlin et al. ). Jobs often ended prematurely because of social or behavioral difficulties or other work-related difficulties (Mawhood and Howlin ).

Young adults on the autism spectrum are reported to experience difficulties in assuming other important adult roles and responsibilities, including attaining postsecondary education and living independently (Roux et al. ). A number of studies (Billstedt et al. ; Gillespie-Lynch et al. ; Howlin et al. ) have found that having an IQ of around 70 seemed to be a critical cutoff point for better outcome (e.g., level of independence). A number of comorbid conditions can complicate the trajectory for youth with intellectual disability through adolescence and EA, such as seizure disorder, which substantially increase in prevalence from childhood through adolescence into adulthood. Adults with ASD and related conditions are more vulnerable to anxiety and depression which can require specific treatments (Skokauskas and Gallagher ; White et al. ). The majority of young adults with ASD remain dependent on parents for support in living, recreation, and occupational situations. The availability of appropriate resources, services, and supports for the individuals with ASD and their families is key for successful transition into adulthood and better outcomes throughout adult life. The following elements are important for high-quality transition services and associated with improved young adult outcomes: (1) individualized services that reflect the strengths of the individual, (2) positive career development and early work experiences, (3) collaboration and interagency involvement, (4) family supports and expectations, (5) fostering self-determination and independence, (6) social and employment-related skill instruction, and (7) establishment of job-related supports. Therefore, outcomes for emerging adults with ASD could be improved if social and institutional supports available through adolescence continued into adulthood.

6.2 Type 1 Diabetes Mellitus (DM)

The study of emerging adults with type 1 DM has elucidated the potential challenges facing emerging adults with diabetes and other chronic health conditions that have significant self-management burden. Emerging adults with type 1 diabetes face extensive behavioral demands in order to maintain their health, including the necessity for precisely scheduled daily insulin injections, blood glucose monitoring, dietary monitoring, regular physical exercise, and the management of DM-related complications. In early adulthood, frequent changes in roles, living situations, educational routines, jobs, friendships, and romantic relationships are common and can undermine the routines and the resolve needed to maintain metabolic control (Anderson and Wolpert ).

The developmental tasks of emerging adulthood may be at odds with maintaining the intensive self-care that is required of those with type 1 diabetes and vice versa. For example, the tasks of establishing autonomy and prevailing egocentrism may be associated with the emerging adult not wanting to follow medical advice or advice of his or her family (Masten et al. ). Heightened concern for peer acceptance or the establishment of intimate relationships is characteristic of this period of development. Emerging adults may be reluctant to admit to their significant others that they have type 1 diabetes or any other chronic condition that puts them at risk for being rejected (Madsen et al. ). Moreover, the major cognitive developmental milestone during the stage of emerging adulthood is the ability to think abstractly (Erikson ). Those who have not yet reached this developmental milestone may struggle with taking responsibility to maintain good disease management understanding the consequences of poor disease management. Lastly, increased rates of drinking, illicit drug use, or other high-risk behaviors may disrupt the emerging adults' lifestyle and negatively impact self-care management of diabetes, resulting in (Madsen et al. ) lack of control of diabetes and the resulting physical and mental consequences of hypo- or hyperglycemia, which undermine emerging adults' abilities to perform in school, maintain relationships, or keep employment.

As has been demonstrated in other chronic childhood conditions, the transition from pediatric- to adult-centered medical care for youth with DM is associated with a decline in DM control (Busse et al. ; Oeffinger et al. ). Adverse health-related outcomes documented in the young adult population with diabetes include a decline in disease self-care behaviors and an increased risk for diabetes-related complications (Bryden et al. ; Fredericks et al. ; Yeung et al. ). In addition, emerging adults with diabetes are at higher than average risk for psychosocial morbidity including social delays and isolation, impaired social competence, and emotional problems such as depression (Helgeson et al. ). As in the case in ASD, additional support for an emerging adult with DM during the transition to adult medical care has been shown to help decrease the adverse outcomes seen with usual practice. For example, DM transition programs that include introductions to new adult care providers or intensive care coordination have been found to be protective (Holmes-Walker et al. ).

6.3 Chronic Kidney Disease

Chronic kidney disease (CKD) is a condition characterized by disease progression, significant cardiovascular morbidity, growth failure, neurocognitive impairment, and impaired quality of life changes (Sarnak ; Copelovitch et al. ; Gerson et al. ; McKenna et al. ). CKD is divided into five stages based on glomerular filtration rate, with stage 1 being the mildest form and stage 5 the worst form, also called end-stage kidney disease (ESKD ), requiring renal replacement therapy (dialysis or transplant) (Hogg et al. ). The prevalence of pediatric CKD is unknown as it may be silent in early stages. The prevalence of pediatric ESKD is 15 cases per million population (Saran et al. ). African-Americans and Latinos are disproportionately affected by CKD in part due to a higher incidence of glomerular conditions (Ferris et al. ). While the 10-year survival for adolescent-onset ESKD is 80-85% (much higher than adult-onset ESKD patients), this still represents a 30-fold increase in mortality compared to the general US adolescent population. Survival is better for younger adolescents, males, Caucasians, Asians, and transplant recipients (). However, emerging adults with CKD achieve adult milestones (e.g., employment, marriage) less frequently than their healthy peers (Bartosh et al. ).

The burden of care directly correlates with the stage of CKD. Based on the mean number of unique medications, those with CKD stages 1-4 take 6.2 ± 4 of medications, those with peritoneal dialysis (CKD 5) take 8.5 ± 2 medications, those with kidney transplant (CKD 5) take 9.7 ± 4.2 medications, and those on hemodialysis (CKD 5) take 11.3 ± 2.1 (So et al. ). The complexity of care also include procedures such as self-catheterization several times per day, fluid and dietary restrictions, blood pressure measurements daily, and injections (erythropoiesis-stimulating agents once to thrice weekly, growth hormone daily, or insulin several times per day). The life course of pediatric-onset CKD-ESKD varies by etiology and age at onset of this condition, but once they reach ESKD, most patients share the same comorbidities (hypertension, anemia, acidosis, metabolic bone disease, and growth delay). Patients with greater level of CKD have a decreased sense of self-worth, perceive a poor future, and feel limited in their physical and psychosocial capacities to have the same potential and opportunity as their healthy peers.

Patients who transfer to adult-focused services without transition preparation and support appear to be at greater risk to lose their kidney transplant (Watson , ). The international societies of internal medicine and pediatric nephrology have published position statements and policies to promote health-care transition preparation (Watson ; Watson et al. ). Strategies to increase patient autonomy, health-care transition, and self-management are needed to achieve successful outcomes at the time of transfer to adult-focused providers.

6.4 Mental Health and Substance Use

Emerging adulthood is a time of increased experimentation with tobacco, drugs, and alcohol (Schulenberg et al. ; Schulenberg and Maggs ), increasing from rates of 12.2% in adolescence to 40.2% in young adulthood for cigarette smoking, from 10.7% to 41.9% for binge drinking, from 11.2% to 20.3% for illicit drug use, and from 2.6% to 14.9% for heavy alcohol use. While cigarette, alcohol, and drug use are normative during adolescence and emerging adulthood, a number of factors predict excessive use rather than experimentation including genetic (e.g., family history of alcohol abuse), biological (e.g., early puberty timing), family (e.g., low parental monitoring), school (e.g., low grade average, school failure), peer (e.g., peer substance use), and youth personality and psychopathology (e.g., depression) factors (Cicchetti ). However, the pattern of use/abuse of these substances is influenced by the experience during the stage of EA. For example, increasing responsibility, work, and marriage all are associated with decreased use of these substances (Masten et al. ; Bachman et al. ). Again, there is great heterogeneity in the trajectories followed by individuals with regard to substance use during this period, all influenced by the multiplicity of factors listed above.

Among young adults, 13.7% experience serious mental illness such as major depressive disorders, schizophrenia, and bipolar disorder (AmericanPsychiatricAssociation ). The neuropsychological pathology that has onset during EA has many of the predisposing factors related to family adversities, such as social disadvantage, divorce, dysfunctional parenting, multiple family changes/moves, and peer group choices. The expanded independence and self-reliance during EA may be difficult to handle for youth with preexisting emotional or social challenges or poor attachment. The decrease in supports from school or family during EA may be even further destabilizing, leading to increased emotional and interpersonal difficulties. Young people with serious mental health conditions have difficulty with impulse control and self-regulation (Walker and Gowen ). Their apparent immaturity reflects a delay in social and emotional development and undermines progress toward goals in education, relationships, independence in health, and health-care management.

Three-quarters of lifetime cases of mental, emotional, and behavioral disorders begin by age 24 (Kessler et al. ). In emerging adults with social, emotional, and behavioral disorders, much higher risk is associated with onset in early adolescence versus onset in late adolescence (Mofitt and Caspi ). Dysfunctional family environments and participation in deviant peer group increase the likelihood of early-onset delinquency followed by a long trajectory of social, emotional, and behavioral problems. Youth with later onset of social, emotional, and behavioral problems are more commonly from relatively healthy family backgrounds and more likely to desist from delinquency by age 23 (Roisman et al. ). Similar patterns can be seen for major psychiatric disorders such as depression, with early-onset mood disorders being representative of more severe recurrent forms of mood disorders arising from increased severity and complexity of family and biologic risk factors (Fergusson and Woodward ) and later-onset disorders reflecting lower levels of risk factors in childhood.

7 Protective and Risk Factors That Impact Emerging Adulthood

The supports, opportunities, and experiences that occur during the stage of EA greatly influence the ultimate outcome of this stage and the ensuing life trajectory into young adulthood. As discussed in this chapter, critical influences during EA include mentoring relationships, socioeconomic supports, and educational and vocational opportunities. Emerging adulthood typically is accompanied by an increase in agency/independence and decrease in social and institutional support (e.g., schools and family), such that most individuals have more choice in day-to-day activities and life decisions. This increase in choice may result in greater success which will likely contribute to well-being. However, increased freedom can result in poor choices (e.g., drug use, criminal activity) that have a negative impact on the developmental trajectory as well (Schulenberg and Maggs ; Schulenberg et al. ). For example, many relationships and other aspects of life are so unstable during EA that important and powerful negative experiences can occur such as date rape, school failure, and substance addiction. These experiences can have a lasting, if not lifetime, detrimental impact on the developmental and mental health trajectory of the emerging adult. Similarly, many potential powerful positive influences can occur during this period in life (e.g., marriage, educational achievement, mentoring) that can enhance the developmental and mental health trajectory. Therefore, experiences both distal (early childhood) and proximal (during emerging adulthood) can influence, either positively or negatively, the developmental and mental health trajectory of the emerging adult (Miller et al. 2015).

Practical supports during EA provided by families include financial support for education, transportation, independent living, health insurance, and other necessities. The primary determinant of parental support are the level of parental resources. Emerging adults with wealthier parents and those with fewer siblings receive more financial support for education (Steelman and Powell ). Divorced parents provide less financial support than parents with intact marriages (Cooney and Uhlenberg ). Support from families by parents and grandparents during EA is also provided in the form of guidance or advice, information, and emotional support. Parents of emerging adults may also help the emerging adult negotiate the health-care system, formulate and carry out educational and vocational goals, and acquire leases for apartments and even provide advice for intimate relationships. In short, continued social and financial connection to parents with adequate emotional and financial resources can be a very significant factor in the positive life trajectory during emerging adulthood (Aquilino ). Previous studies have found a high correlation between improved EA outcomes and adolescent hope in the future (Bennett ). Hope is a form of personal capital that protects youth from social, emotional, and behavioral disorders and correlates with and predicts the rates of many outcomes, including academic achievement, delay of initiation of early sexual activity, and lower likelihood of violent behavior. Hope requires a sense of self-efficacy and knowledge of alternate outcomes. Hope is reflected in adolescent and young adult goals as they reflect and make ongoing assessments of their current and future selves. Individual goals and aspirations relate to the sense of control an individual feels in relation to a particular domain.

Positive youth development (PYD) programs are approaches that provide supports to adolescents and emerging adults to achieve social, emotional, behavioral, and moral competence, foster self-efficacy, a clear and positive identity, and belief in the future; and reinforce pro-social norms (Catalano et al. ). Positive development approaches involve a paradigm shift from targeting the risk factors to enhancing the assets and protective factors. The emphasis on hope, empowerment, and well-being resonates with youth and mental health professionals. The PYD approach outlined above suggests that effective programs to support EA would include an individualized approach supporting young people to identify and move toward personally meaningful goals. This begins with envisioning a positive future identity ("Who do I want to become?"). Pursuing goals promotes a sense of purpose, and making progress toward those goals contributes to building feelings of efficacy, empowerment, and self-determination, enhancing the individual's ability to act as the primary causal agent in pursuing personally meaningful goals (Silbereisen and Lerner ).

A PYD perspective further suggests that youth and emerging adults will benefit from learning specific strategies for increasing and maintaining interpersonal support from positive peers, family, providers, and people in the community (Guerra and Bradshaw ). Young people can learn specific steps and skills that can help them increase the quality and the extent of their interpersonal networks, as well as the amount of emotional, instrumental, and informational support available to them. Using a PYD perspective suggests that the development of assets is an important recovery-oriented outcome in and of themselves, as well as a mediator of longer-term outcomes related to education, employment, mental health, and general quality of life. Indeed, a review of the available research on community-based programs and interventions for EA reveals a common focus on personal asset building (Lerner ). Also consistent with the PYD perspective is that many of the programs and interventions include a focus on changing the meso-environment of youth so that it encourages young people to develop or express strengths and assets.

8 Services and Supports

As we better understand the limits of and issues related to EA, it is imperative that we review and revise policy and current social and medical services and supports so they optimally address the current and future needs of individuals during this life stage. Current medical, mental health, and social service delivery models are geared toward either child or adult populations. In other words, individuals generally seek child-serving services between the ages of 0 and 18, and they are subsequently transferred directly to adult-serving services. However, the various biobehavioral and sociocultural factors discussed above make this direct transition from child to adult-centered care ill-suited for optimally addressing the nuances and challenges that individuals may face during EA. For example, an adult-centered medical doctor may regularly treat patients with fixed habits and lifestyles, who may already suffer from a variety of chronic health conditions. However, many such chronic health conditions in adults represent a culmination of experiences from an individual's earlier years, which may not yet be apparent during EA. It is thus strongly recommended that EA service providers reorient themselves using a prevention-based paradigm and familiarize themselves with the possible antecedents to social, emotional, and medical conditions so that they may make health-care or social service recommendations to minimize risk factors and to maximize strengths and assets to facilitate development along optimal health trajectories. EA presents a unique opportunity for service providers to intervene and influence an individual's LCHD before significant social, emotional, and medical pathology fully develops, utilizing existing knowledge of the skills and capacities associated with EA to inform services and interventions.

In addition to training service providers to reorient their approach to care and become more sensitive to antecedents of chronic health conditions in adulthood, the multifactorial nature of the LCHD model suggests that it would be important for service providers to consider horizontal (i.e., cross sector) and longitudinal (i.e., across the lifespan) service integration. Specifically, the current model posits that myriad factors (e.g., biological, psychological, cultural) on multiple levels (e.g., micro, meso, macro) interact simultaneously in a transactional fashion to influence an individual's LCHD and overall health trajectory. However, most current training models which emphasize specialization in their independent fields and opportunities for cross-disciplinary case conceptualization and collaboration with regard to service delivery - particularly with respect to preventive care, which may be of special importance when considering EA as a sensitive period of development - tend to be rare. Such specialization in service delivery may result in service fragmentation. Additionally, adult service providers generally do not work in tandem with child service providers as individuals transition from one care setting to the next, consequently resulting in potential gaps in service delivery and care, which may be exacerbated as individuals work to rebuild rapport with their new service providers. Moreover, health, mental health, social service, and education professionals rarely collaborate to create comprehensive models across the EA stage. Clearly, the current service delivery infrastructure does not adequately support the needs and challenges unique to emerging adult populations. It is thus important to recognize emerging adults as a unique population requiring additional and specialized skills of service providers and the creation of specific pathways for transition which support continuity of care.

The larger sociopolitical and cultural contexts may also facilitate or create challenges which impact service and intervention efforts directed at emerging adults. The majority of individuals in developed nations transitioning through EA, for instance, may be classified as "digital natives ," individuals who have been brought up in environments where exposure to digital technology may be normative and who are therefore familiar with computers and the Internet. As emerging adults increasingly turn to digital and mobile solutions to support and enhance their daily routines, it behooves service providers to creatively explore ways of engaging emerging adult populations using technology. Use of social networks, such as Instagram, Twitter, and Facebook, to advance primary prevention efforts, increase awareness of public health issues, and provide basic health and psychological education affords service providers the opportunity to outreach to unprecedented numbers and populations. Use of text messaging may also be effective as a way of engaging with digital native emerging adult populations and promoting engagement and adherence by emerging adults or to promote youth development programs. Also, as service providers keep pace with technological advancements, they may even begin to explore novel methods of service delivery and intervention using digital or Internet-based platforms, which may increase "buy-in" and potentially preventive service utilization, among digitally native emerging adult populations. For example, service providers might potentially leverage the data that digitally native emerging adults might collect as part of the "quantified self" movement (e.g., pedometer information, weight, blood pressure, etc.) in an effort to inform their ongoing care efforts.

On the other hand, due to clinical billing practices and regulations, as well as patient privacy concerns and regulations (e.g., Health Insurance Portability and Accountability Act, HIPAA), current service delivery models often tend to operate in a fragmented and siloed fashion, which in turn may limit the ability of service providers to develop a holistic treatment plan to address each individual's needs. Further complicating this fragmentation is the restricted access to health records once an individual turns 18 years of age, when parents who may have been primarily responsible for managing their child's health-care needs no longer are able to access their child's medical records (unless explicit permission is granted by the child, who is now an emerging adult). Depending on each family's cultural context and the relationship between the emerging adult and his or her parents, this transition may be a cause for significant stress and/or strife between family members as they work to renegotiate previously familiar boundaries. Mothers of children with diabetes, for example, have indicated feeling increased stress as their children transitioned from pediatric to adult care, particularly if they perceived that their children were not managing their health-care condition as well as they had been when it was previously under greater parent control (Allen et al. ). Such stress might result in familial conflict and dysfunction which could subsequently interfere with the emerging adult's willingness or ability to adequately access services. One potential solution to overcoming the issue of patient privacy may be to implement public health programs and tools to educate and empower individuals with respect to managing and taking an active role in their own care. However, it is important to underscore the need for larger, overall systems to change in order to support service providers in working together with individuals and their families to ensure continuity and comprehensiveness of services and health-related information during the transition.

Finally, the implementation of health-care policies may have important implications for service and intervention delivery with an emerging adult population. With the introduction of the Patient Protection and Affordable Care Act of 2010 (ACA), for example, individuals may now remain on their parents' health insurance plans until they turn 26 years of age. While this theoretically affords emerging adults the opportunity to develop the necessary skills for interacting with the health-care system and managing their own care, research indicates that emerging adults frequently perceived themselves as being at lower risk for health problems and the financial burden of health insurance as lacking in value. Consequently, emerging adults may opt for high-deductible catastrophic insurance which generally costs less compared to other health insurance plans, but translates to fewer opportunities for interaction with the health service sector and fewer opportunities for service providers to intervene early during an individual's LCHD trajectory prior to the onset of chronic adult disease. Importantly, research indicates that despite preventive maintenance health visits being mandatory under the ACA, emerging adults were less likely to request health maintenance visits. Thus, it may be important for public health efforts to determine the underlying factors associated with this diminished utilization of health services by emerging adults and subsequently develop health literacy programs to promote prevention mindedness and service utilization in emerging adults.

9 Recommendations for Research Priorities

The following is a list of issues in life course research that are critical for better understanding the positive supports and challenges that influence the trajectory of development of emerging adults organized along the macro-, meso-, micro-framework.

What factors promote resilience for youth during EA who lack family supports?

What is the role of extended families in support for EA?

How can studies of conditions and processes that influence development during EA inform educational/vocational/EA support policies?

How can data be gathered across this stage in the lifespan given that emerging adults leave school and have many changes in living arrangements, education, relationships, and work?

# data[].attributes.attachment_link.title
Emerging Adulthood as a Critical Stage in the Life Course

# data[].attributes.attachment_link.description
David Wood Tara Crapnell Lynette Lau Ashley Bennett Debra Lotstein Maria Ferris Alice Kuo The path that individuals take from dependency in childhood to independence in adulthood is now a longer and more complicated one than at any other point in history (Arnett ).

# data[].attributes.attachment_link.readable_text
Physical Development in Adulthood

As individuals move through early and middle adulthood, a variety of physical changes take place in the body.

Learning Objectives

Review the milestones of physical development in early and middle adulthood

Key Takeaways

Key Points

Adults experiences age-related changes based on many factors: biological factors such as molecular and cellular changes are called primary aging, while aging that occurs due to controllable factors, such as lack of physical exercise and poor diet, is called secondary aging.

In early adulthood (ages 20-40), our physical abilities are at their peak, including muscle strength, reaction time, sensory abilities, and cardiac functioning.

The aging process also begins during early adulthood and is characterized by changes in skin, vision, and reproductive capability.

Aging speeds up during middle adulthood (ages 40-65) and is characterized by decline in vision, hearing, and immune-system functioning, as well as the end of reproductive capability for women, known as menopause.

Key Terms

glaucoma: An eye disease or disorder of the optic nerve that, if untreated, may lead to damage to the optic disc of the eye and resultant visual-field loss, which can lead to blindness.

menopause: The ending of menstruation; the time in a woman's life when this happens.

presbyopia: Inability of the eye, due to aging, to focus on nearby objects; farsightedness.

As we age, our bodies change in physical ways. One can expect a variety of changes to take place through the early- and middle-adult years. Each person experiences age-related changes based on many factors: biological factors such as molecular and cellular changes are called primary aging, while aging that occurs due to controllable factors, such as lack of physical exercise and poor diet, is called secondary aging.

Early Adulthood (Ages 20-40)

By the time we reach early adulthood, our physical maturation is complete, although our height and weight may increase slightly. In early adulthood, our physical abilities are at their peak, including muscle strength, reaction time, sensory abilities, and cardiac functioning. Most professional athletes are at the top of their game during this stage, and many women have children in the early-adulthood years.

The aging process, although not overt, begins during early adulthood. Around the age of 30, many changes begin to occur in different parts of the body. For example, the lens of the eye starts to stiffen and thicken, resulting in changes in vision (usually affecting the ability to focus on close objects). Sensitivity to sound decreases; this happens twice as quickly for men as for women. Hair can start to thin and become gray around the age of 35, although this may happen earlier for some individuals and later for others. The skin becomes drier and wrinkles start to appear by the end of early adulthood. The immune system becomes less adept at fighting off illness, and reproductive capacity starts to decline.

Middle Adulthood (Ages 40-65)

During middle adulthood, the aging process becomes more apparent. Around the age of 60, the eyes lose their ability to adjust to objects at varying distances, known as presbyopia. Most people between the ages of 40 and 60 will need some form of corrective lenses for vision deficits. Middle-aged adults are also at higher risk than younger adults for certain eye problems, such as glaucoma. Hearing also further declines: 14 percent of middle-aged Americans have hearing problems. Skin continues to dry out and is prone to more wrinkling, particularly on the sensitive face area. Age spots and blood vessels become more apparent as the skin continues to dry and get thinner. The muscle-to-fat ratio for both men and women also changes throughout middle adulthood, with an accumulation of fat in the stomach area.

Women experience a gradual decline in fertility as they approach the onset of menopause-the end of the menstrual cycle-around 50 years old. This process involves hormonal changes and may last anywhere from six months to five years. Because of the shifting hormone levels, women going through menopause often experience a range of other symptoms, such as anxiety, poor memory, inability to concentrate, depressive mood, irritability, mood swings, and less interest in sexual activity.

Cognitive Development in Adulthood

Cognition changes over a person's lifespan, peaking at around age 35 and slowly declining in later adulthood.

Learning Objectives

Review the milestones of cognitive development in early and middle adulthood

Key Takeaways

Key Points

Unlike our physical abilities, which peak in our mid-20s and then begin a slow decline, our cognitive abilities remain relatively steady throughout early and middle adulthood.

Since Piaget's theory of cognitive development, other developmental psychologists have suggested a fifth stage of cognitive development, known as postformal operational thinking.

Early adulthood is a time of relativistic thinking, in which young people begin to become aware of more complexities in life.

Two forms of intelligence -crystallized and fluid-are the main focus of middle adulthood. While crystallized intelligence grows steadily, fluid intelligence starts to decline even prior to mid-adulthood.

Key Terms

dialectic: Any formal system of reasoning that arrives at a truth by the exchange of logical arguments; a contradiction of ideas that serves as the determining factor in their interaction.

constructive: Carefully considered and meant to be helpful.

contradiction: A logical incompatibility among two or more elements or propositions.

Because we spend so many years in adulthood (more than any other stage), cognitive changes are numerous during this period. In fact, research suggests that adult cognitive development is a complex, ever-changing process that may be even more active than cognitive development in infancy and early childhood (Fischer, Yan, & Stewart, 2003).

Unlike our physical abilities, which peak in our mid-20s and then begin a slow decline, our cognitive abilities remain relatively steady throughout early and middle adulthood. Research has found that adults who engage in mentally and physically stimulating activities experience less cognitive decline in later adult years and have a reduced incidence of mild cognitive impairment and dementia (Hertzog, Kramer, Wilson, & Lindenberger, 2009; Larson et al., 2006; Podewils et al., 2005).

Beyond Piaget's Theory

According to Jean Piaget's theory of cognitive development, the establishment of formal operational thinking occurs during early adolescence and continues through adulthood. Unlike earlier concrete thinking, this kind of thinking is characterized by the ability to think in abstract ways, engage in deductive reasoning, and create hypothetical ideas to explain various concepts.

Since Piaget's theory, other developmental psychologists have suggested a fifth stage of cognitive development, known as postformal operational thinking (Basseches, 1984; Commons & Bresette, 2006; Sinnott, 1998). In postformal thinking, decisions are made based on situations and circumstances, and logic is integrated with emotion as adults develop principles that depend on contexts. This kind of thinking includes the ability to think in dialectics, and differentiates between the ways in which adults and adolescents are able to cognitively handle emotionally charged situations.

Early Adulthood

During early adulthood, cognition begins to stabilize, reaching a peak around the age of 35. Early adulthood is a time of relativistic thinking, in which young people begin to become aware of more than simplistic views of right vs. wrong. They begin to look at ideas and concepts from multiple angles and understand that a question can have more than one right (or wrong) answer. The need for specialization results in pragmatic thinking-using logic to solve real-world problems while accepting contradiction, imperfection, and other issues. Finally, young adults develop a sort of expertise in either education or career, which further enhances problem-solving skills and the capacity for creativity.

Middle Adulthood

Two forms of intelligence-crystallized and fluid-are the main focus of middle adulthood. Our crystallized intelligence is dependent upon accumulated knowledge and experience-it is the information, skills, and strategies we have gathered throughout our lifetime. This kind of intelligence tends to hold steady as we age-in fact, it may even improve. For example, adults show relatively stable to increasing scores on intelligence tests until their mid-30s to mid-50s (Bayley & Oden, 1955). Fluid intelligence, on the other hand, is more dependent on basic information-processing skills and starts to decline even prior to middle adulthood. Cognitive processing speed slows down during this stage of life, as does the ability to solve problems and divide attention. However, practical problem-solving skills tend to increase. These skills are necessary to solve real-world problems and figure out how to best achieve a desired goal.

Socioemotional Development in Adulthood

Early and middle adulthood is influenced by a number of social and emotional factors, such as work and interpersonal relationships.

Learning Objectives

Review the milestones and crises of socioemotional development in early and middle adulthood

Key Takeaways

Key Points

There are many social and emotional factors that influence aging. For those in early and middle adulthood, meaning is often found through work and family life-two areas that correspond with Erik Erikson's psychosocial theory of development.

According to Erikson, intimacy vs. isolation is a stage of psychosocial development in which people face the crisis of being alone versus being involved in meaningful relationships.

Positive relationships with significant others in our adult years have been found to contribute to a state of well-being.

Erikson's stage of generativity vs. stagnation revolves around a person's sense of their contribution to the world.

Central tasks during middle adulthood can include maintaining healthy life patterns, raising children or in some way helping future generations, being proud of one's accomplishments, or taking care of aging parents.

Key Terms

generativity: Contributing to the development of others and of future generations; productivity and creativity; the act of helping society move forward.

Social and Emotional Aspects of Adulthood

There are many theories about the social and emotional aspects of aging. Some aspects of healthy aging include activities, social connectedness, and the role of a person's culture. According to many theorists, including George Vaillant (2002), who studied and analyzed over 50 years of data, we need to have and continue to find meaning throughout our lives.

For those in early and middle adulthood, meaning is often found through work (Sterns & Huyck, 2001) and family life (Markus, Ryff, Curan, & Palmersheim, 2004). These areas relate to the tasks that Erik Erikson referred to as generativity vs. stagnation and intimacy vs. isolation.

Relationships in Adulthood

Positive relationships with significant others in our adult years have been found to contribute to a state of well-being (Ryff & Singer, 2009). Most adults in the United States identify themselves through their relationships with family-particularly with spouses, children, and parents (Markus et al., 2004). While raising children can be stressful, especially when they are young, research suggests that parents reap the rewards down the road, as adult children tend to have a positive effect on parental well-being (Umberson, Pudrovska, & Reczek, 2010). Having stable intimate relationships has also been found to contribute to well-being throughout adulthood (Vaillant, 2002).

A lack of positive and meaningful relationships during adulthood can result in what Erikson termed the crisis of intimacy vs. isolation in his theory of psychosocial development. In young adulthood (i.e., 20s and early 30s), people tend to be concerned with forming meaningful relationships; young and middle-aged adults are subject to loneliness if they are unable to form meaningful relationships with family, friends, or community.

Crises of Adulthood

Both early and middle adulthood come with particular challenges; these challenges are at times referred to as "quarter-life crises" and " mid-life crises," respectively. A quarter-life crisis typically occurs between the ages of 25 and 30. It often revolves around the challenges that arise from young adults newly living life on their own and feeling overwhelmed with new responsibilities; it can also happen after the birth of a child or if a person graduates from college and cannot find a job in their chosen field. In this stage of life, young people may worry about their future, wonder if they've made poor choices, or wonder what life might hold for them now.

The main triggers for a mid-life crisis include problems with work, trouble in a marriage, children growing up and leaving the home, or the aging or death of a person's parents. This is likely to occur during Erikson's stage of generativity vs. stagnation, a time when people think about the contribution they are making to the world. Generativity involves finding one's life's work and contributing to the development of others through activities such as volunteering, mentoring, and raising children; those who do not master this task may experience a feeling of stagnation.

Individuals having a mid-life crisis may experience some of the following:

a search for an undefined dream or goal;

a deep sense of regret for goals not accomplished;

a fear of humiliation among more successful colleagues;

a desire to achieve a feeling of youthfulness;

a need to spend more time alone or with certain peers.

Some who experience a quarter- or mid-life crisis struggle with how to cope and may engage in harmful behaviors, such as abuse of alcohol or drugs or excessive spending of money. Others may experiment with different aspects of their personality, explore new hobbies, or otherwise seek out change in their lives.

Finding Meaning Through Work

Many adults find meaning in and define themselves by what they do-their careers. Earnings peak for many during adulthood, yet research has found that job satisfaction is more closely tied to work that involves contact with other people, is interesting, provides opportunities for advancement, and allows some independence (Mohr & Zoghi, 2006) than it is to salary (Iyengar, Wells, & Schwartz, 2006).

Erikson's stage of generativity vs. stagnation revolves around a person's sense of their contribution to the world. Generativity is about making life productive and creative so that it matters to others, especially those in the next generation. According to Erikson, a person who is self-centered and unable or unwilling to help society move forward develops a feeling of stagnation-a dissatisfaction with the relative lack of productivity. The central tasks during middle adulthood can include expressing love through more than sexual contacts, maintaining healthy life patterns, helping growing and grown children to be responsible adults, relinquishing a central role in the lives of grown children, creating a comfortable home, being proud of one's accomplishments, taking care of aging parents, adjusting to the physical changes of middle age, and using leisure time creatively.

Relationships and Families in Adulthood

Several theories examine how interpersonal relationships form and develop during adulthood.

Learning Objectives

Summarize Levinger's and Knapp's theories of relational development in adulthood

Key Takeaways

Key Points

An interpersonal relationship is a strong, deep, or close association or acquaintanceship between two or more people that may range from brief to enduring in duration.

Interpersonal relationships are dynamic systems that change continuously during their existence. Like living organisms, relationships have a beginning, a lifespan, and an end.

One of the most influential models of relationship development was proposed by psychologist George Levinger. His model consists of five stages: acquaintanceship, buildup, continuation, deterioration, and termination.

M. L. Knapp developed a model of relational development, consisting of two main stages: the coming-together stage and coming-apart stage.

Coming together consists of five phases-initiating, experimentation, intensifying, integration, and bonding. Similarly, coming apart consists of differentiating, circumscribing, stagnation, avoidance, and termination.

Key Terms

interpersonal: Existing between two or more people.

heterosexual: Sexually attracted to members of the opposite sex.

Interpersonal Relationships in Adulthood

Positive relationships with significant others in our adult years have been found to contribute to a state of well-being (Ryff & Singer, 2009). Most adults in the United States identify themselves through their relationships with family-particularly with spouses, children, and parents. An interpersonal relationship is a strong, deep, or close association or acquaintanceship between two or more people that may range from brief to enduring in duration. Like people, relationships change and grow; they may either improve or dissipate over time. The association between two people can be based on various factors-love, solidarity, business, or any other context that requires two (or more) people to interact.

Interpersonal relationships are dynamic systems that change continuously during their existence. Like living organisms, relationships have a beginning, a lifespan, and an end. They tend to grow and improve gradually as people get to know each other and become closer emotionally, or they gradually deteriorate as people drift apart.

Levinger's Model of Relationships

One of the most influential models of relationship development was proposed by psychologist George Levinger. This model was formulated to describe heterosexual, adult romantic relationships, but it has been applied to other kinds of interpersonal relationships since then. According to the model, the natural development of a relationship follows five stages:

1. Acquaintance and Acquaintanceship: Becoming acquainted depends on previous relationships, physical proximity, first impressions, and a variety of other factors. If two people begin to like each other, continued interactions may lead to the next stage, but acquaintance can continue indefinitely. Another example is association.

2. Buildup: During this stage, people begin to trust and care about each other. The need for intimacy, compatibility, and such filtering agents as common background and goals will influence whether or not interaction continues.

3. Continuation: This stage follows a mutual commitment to strong and close long-term friendships, romantic relationship, or even marriage. It is generally a long, relatively stable period. Nevertheless, continued growth and development will occur during this time. Mutual trust is important for sustaining the relationship.

4. Deterioration: Not all relationships deteriorate, but those that do tend to show signs of trouble. Boredom, resentment, and dissatisfaction may occur. Individuals may communicate less and avoid self-disclosure. Loss of trust and betrayals may take place as the downward spiral continues, eventually ending the relationship. Alternately, the participants may find some way to resolve the problems and reestablish trust.

5. Termination: The final stage marks the end of the relationship, either by breakup, death, or spatial separation and severing all existing ties of either friendship or romantic love.

Knapp's Theory of Relational Development

Another theory, developed by M. L. Knapp, is known as the model of relational development. This theory consists of two main stages, each with several parts. The first stage is known as the coming together phase, and the second stage is known as the coming apart phase.

Coming Together

Coming together consists of five phases- initiating, experimentation, intensifying, integration, and bonding.

1. During initiating, first impressions are made; physical factors play a large role in this phase. People often want to portray themselves as easy to talk to, friendly, and open to discussion. This phase tends to be superficial as people are trying to make a good first impression.

2. During experimentation, the two people attempt to find some common ground between each other's lives, such as common interests and hobbies. People start to open up more and ask more personal questions as they get to know one another.

3. During the intensifying phase, people open themselves up fully in the hope of being accepted by the potential mate. During this phase, people may reveal secrets about themselves or others in order to test the trust level of potential partners.

4. The integration phase involves people merging their lives together and solidifying a relationship status.

5. Finally, during the bonding phase, people recognize a commitment to one another (traditionally through marriage, though many alternative forms of commitment exist) and the relationship lasts until death, breakup, or divorce.

Coming Apart

Coming apart consists of five stages as well- differentiating, circumscribing, stagnation, avoidance, and termination.

1. Differentiation involves focusing more on differences rather than similarities. This can lead to an increasing emotional distance between the parties involved.

2. During circumscribing, the primary focus of the relationship shifts from differences to setting limits and boundaries on communication between the two people. This further pushes two people apart.

3. Stagnation is when two people have reached a "stand-off" phase-nothing changes and neither party is willing to change.

4. Avoidance occurs when people engage in limited communication and take steps to distance themselves from one another.

5. Finally, during termination, the relationship is ended.

# data[].attributes.attachment_link.description
As individuals move through early and middle adulthood, a variety of physical changes take place in the body. Review the milestones of physical development in early and middle adulthood Key Points Adults experiences age-related changes based on many factors: biological factors such as molecular and cellular changes are called primary aging, while aging that occurs due to controllable factors, such as lack of physical exercise and poor diet, is called secondary aging.

# data[].attributes.body
https://www-sciencedirect-com.lopes.idm.oclc.org/science/article/pii/S1053811918300089

# data[].attributes.headline
Physical and Cognitive development through Middle Adulthood

# data[].attributes.subject
Physical and Cognitive development through Middle Adulthood

# data[].attributes.attachment_link.readable_text
Chapter 15
Physical and Cognitive Development in Middle Adulthood

Physical Development in Middle Adulthood

Middle adulthood is the time when most people first become aware of the gradual changes in their bodies that mark the aging process.

Declines also occur in depth perception, distance perception, the ability to view the world in three dimensions, and night vision.

Hearing in Middle Age

Reaction time in Middle Age

There are differences in the sexual experiences of people in middle adulthood...

The Female Climacteric & Menopause

Starting about age 45, women enter a period known as the FEMALE CLIMACTERIC, the transition from being able to bear children to being unable to do so.

The most notable sign is MENOPAUSE, the cessation of menstruation, considered to have occurred after one year without menstrual periods.

Symptoms

Hormone production may fluctuate widely in perimenopause.
.
Symptoms of menopause differ by race/ethnicity

The Psychological Consequences of Menopause

Historically, it was thought that about 10 % of women had psychological problems associated with menopause:

The Male Climacteric

The Male Climacteric

The most common is the enlargement of the prostate gland.

Health in Middle Age

Health in Middle Age, continued

Social and environmental factors are related to health: African-Americans in the U.S. have twice the death rate of Caucasians.

Ethnic and Gender Variations in Health
(continued)

The ABC's of Heart Disease in Middle Adulthood

More men die in middle age of diseases of the heart and circulatory system than any other cause.

Environmental and behavioral risk factors:

Men are more likely to suffer than women, and risks increase with age.

Type A behavior, continued

They engage in polyphasic activities - multiple activities carried out simultaneously.

Type B's and heart attack risk

By contrast, people with TYPE B BEHAVIOR PATTERN, which is characterized by noncompetitiveness, patience, and a lack of aggression, have less than half the risk of coronary disease that Type A people have.

Not all type A's are destined to suffer heart disease.

The Threat of Cancer

Cancer (unchecked cell growth) is the second leading cause of death in middle age.

Cancer, continued

Early diagnosis of cancer is crucial.

The earlier that breast cancer is diagnosed, the better a woman's chance of survival

Psychological Factors Related to Cancer

Cognitive Development
Does intelligence decline with age?

Cross-sectional studies - which test people of different ages at the same point in time - clearly showed that older subjects scored less well than younger subjects on traditional IQ tests.

Cognitive Development, continued

Cognitive Development, continued

Longitudinal studies, in which the same people are studied periodically over a span of time, revealed different developmental patterns in intelligence.

Results of assessments of intelligence are complicated by the fact that many IQ tests include a physical performance portion.

Crystallized & Fluid Intelligence

Many researchers believe there are two kinds of intelligence.

Competence during middle adulthood: Reframing the issue

Even though scores on IQ tests decline with age, middle-aged people show no decline in general cognitive competence.

Professional success may not rely exclusively on cognitive ability.

Memory in Middle Adulthood

According to research on memory changes in adulthood, most people show only minimal losses, and many exhibit no memory loss in middle adulthood.

Memory in middle adulthood, continued

Sensory memory is an initial, momentary storage of information that lasts only an instant.

Memory Schemas

We recall information through use of SCHEMAS, organized bodies of information stored in memory.

MNEMONICS

Schemas allow people to organize, categorize, and interpret new information.

Schemas allow people to organize their life into coherent wholes and interpret social events.

Material that is consistent with existing schemas is more likely to be recalled than material that is inconsistent.

Mnemonics, continued

Encoding specificity phenomenon is the principle that people are most likely to recall information in environments that are similar to those in which the information was initially learned.

Memory, continued

People's previous experiences within the context of a particular culture allow the construction of schemas in memory as tools for interpreting new encounters

Schemas, in turn, allow people to comprehend & interpret new encounters

Memory schemas influence people's recall of new information

Material that is consistent with schemas is more likely to be recalled.

The keyword technique is when the learner forms a mental picture of something and connects it to something to be remembered.

Rehearsal is the idea that practice makes perfect.

No decline in middle age.

Short-term memory holds information for 15 to 25 seconds.

No decline in middle age.

Long-term memory holds information that is rehearsed for a relatively permanent time.

Some decline in middle age.

Storage is less efficient.

A reduction in efficiency of memory retrieval.

Memory is viewed in terms of three sequential components.

Older, successful people may have developed expertise in their particular occupational area or SELECTIVE OPTIMIZATION, the process by which people concentrate on particular skill areas to compensate for losses in other areas.

Traditional tests may not tap into practical intelligence.

Highly successful middle-aged people may not be representative of all middle-aged people.

FLUID INTELLIGENCE is the ability to deal with new problems and situations.

Fluid intelligence is inductive reasoning, spatial orientation, perceptual speed, and verbal memory.

Fluid intelligence does decline with age.

Crystallized & Fluid Intelligence, continued

CRYSTALLIZED INTELLIGENCE is the store of information, skills, and strategies that people have acquired through education and prior experiences, and through their previous use of fluid intelligence.

Crystallized intelligence includes numerical and verbal abilities, such as solving a crossword puzzle or a mathematical problem.

Crystallized intelligence holds steady or increases with age.

These are timed.

Reaction time slows with age.

Results may be due to physical changes not cognitive changes

Adults showed stable and even increasing IQ scores until mid-30s and some to mid-50s, then declined.

Subjects leave or die during time span; those who remain may be healthier, more stable, and psychologically more positive than the people who dropped out.

Longitudinal studies may overestimate the intelligence of older people.

These studies suffer from the cohort effect - influences associated with growing up at a particular historical time that affect people of a particular age.

may be less educated

may have less stimulation on job

may have poorer health

Cross-sectional studies may underestimate intelligence in older subjects.

Intelligence peaks at 18, stays steady until mid-20s, and declines till end of life.

Increasing evidence suggests that cancer is related to psychological factors, also.

The death rate of women with breast cancer was much lower for those who had a "fighting spirit" or those who denied they had the disease.

People with close family ties are less likely to develop cancer.

Cancer patients who are habitually optimistic report less physical and psychological distress.

Mammography, a weak X-ray, is used to detect breast cancer.

Women over 40 should routinely have one.

Younger women have denser breasts and the problem of false positives increases, which is one reason younger women are not encouraged to have testing done.

Treatment of cancer can take a variety of forms.

Radiation therapy involves the use of radiation to destroy a tumor.

Chemotherapy involves the controlled ingestion of toxic substances meant to poison the tumor.

Surgery may be used to remove the tumor.

Many forms of cancer respond well to treatment.

40 % are still alive 5 years after diagnosis.

Cancer is associated with several risk factors.

Genetics (family history of cancer) raises the risk.

Poor nutrition, smoking, alcohol use, exposure to sunlight, exposure to radiation, and exposure to occupational hazards such as certain chemicals raises the risk

They can learn to behave differently

They are easily angered and become verbally and nonverbally hostile if prevented from reaching their goals. Hostility is thought to be the major link to heart disease.

Heart rate and blood pressure rise, epinephrine and norepinephrine increase.

Wear and tear on heart produces disease.

Evidence is only correlational so we cannot say Type A behavior causes heart disease. Also, research is on men.

The Type A's and Type B's

Evidence suggests that some psychological factors are also related to heart disease.

People with TYPE A BEHAVIOR PATTERN, which is characterized by competitiveness, impatience, and a tendency toward frustration and hostility, are more susceptible to heart disease.

Cigarette smoking

High fat and cholesterol in diet

Lack of physical exercise

Both genetic and experiential factors are involved.

Heart disease runs in families.

Gender, like SES, makes a difference in health.

Women more likely to experience minor, short-term illness and diseases like migraine headaches.

Men more apt to experience heart disease.

Men more susceptible to cancer, heart disease, liver disease, and accidents.

More medical research is geared toward men's health.

Stress in Middle Adulthood

Stress continues to significantly impact health during middle adulthood.

Stressors themselves may be different.

Related to SES (socioeconomic status): When death rates are compared for whites and African-Americans of the same SES, African-Americans' death rate drops below whites'.

Poorer people are more apt to experience a disabling illness.

Poorer people tend to work in more dangerous occupations & are more likely to become disabled.

Despite this, surveys show that health issues are a major concern to middle aged adults.

Some chronic diseases do begin to appear in middle adulthood.

Arthritis typically begins after age 40.

Diabetes is most likely to occur in people between the ages of 50 and 60.

Hypertension (high blood pressure) is one of the most frequent chronic disorders found in middle age.

The death rate for people between 40 and 60 has declined dramatically; it is less than half of what it was in 1940.

Health concerns become increasingly important to people during middle adulthood.

The vast majority of people in middle age face no chronic health difficulties and have fewer accidents and infections because they are more careful and have built up immunities over their life.

By age 40, 10 percent of men have enlarged prostates. (50% by age 80)

Erectile dysfunction is also more common, and may be caused by medical problems, medication side effects, or psychological issues.

Men still produce sperm and can father children through middle age.

Do men experience the equivalent of menopause? Not really.

Since they haven't experienced anything like menstruation, no similar large scale change.

Men do experience some changes during middle age that are collectively referred to as the MALE CLIMACTERIC, the period of physical and psychological change relating to the male reproductive system that occurs during late middle age.

depression

anxiety

crying spells

lack of concentration

irritability

It is now believed that women's expectations about menopause relate to their experience of menopause, but hormonal fluctuations can also cause mood symptoms.

Japanese & Chinese women: fewer symptoms.

African-American women: more hot flashes & night sweats.

Hispanic women: higher level of heart pounding & vaginal dryness.

Reasons unclear: systematic physical differences in hormone production levels suspected. Diet may be part of this.

In menopause, the production of estrogen and progesterone drop.

Symptoms such as "hot flashes," headaches, feeling dizzy, heart palpitations, and aching joints are common during this time.

Half of women report no symptoms at all

The average age of menopause is about 51.

Perimenopause refers to changes in hormones beginning about 10 years prior to menopause.

Men typically need more time to get an erection.

The volume of fluid in ejaculation declines.

The production of testosterone also declines.

In women, hormonal changes during menopause can cause the walls of the vagina to become less elastic and thinner and the vagina to shrink, potentially making intercourse painful for some women.

Reaction time increases slightly in middle adulthood.

This is due to a gradual loss of muscle in the body and slower nervous system processing due to aging.

People can compensate by being more careful and practicing skills.

Exercise can slow this loss.

The Ongoing Sexuality of Middle Age

Contrary to popular stereotypes, sexual activity does not fade away for most middle age adults.

Although the frequency of sexual intercourse decreases with age, sexual activities remain a vital part of most middle-aged adults' lives.

With children grown and away from home, middle-aged adults have more freedom for sexual enjoyment.

With menopause, couples no longer need to practice birth control.

Hearing undergoes a gradual decline beginning in middle adulthood.

The primary sort of loss is for sounds of high frequency, a problem called PRESBYCUSIS.

About 12 percent of people between 45 and 65 suffer from presbycusis.

Men are more prone to hearing loss than women.

Hearing in Middle Age, continued

Because the two ears are not always equally affected by hearing loss, sound localization, the ability to detect the origin of a sound, is diminished.

Some hearing loss results from environmental factors, such as loud noises.

The rest are caused by aging, which brings a loss of hair cells in the inner ear.

Also, the ear drum becomes less elastic with age.

Sometimes changes in vision are brought on by a disease called GLAUCOMA, a condition where pressure in the fluid of the eye increases, either because the fluid cannot drain properly or because too much fluid is produced.

About 1 percent to 2 percent of those over 40 are affected.

African-Americans are particularly susceptible.

It can be treated if caught early enough.

If left untreated it can cause blindness.

Western society applies a double standard to men and women in terms of appearance.

Older women tend to be viewed in unflattering terms.

Aging men are more frequently perceived as displaying a maturity that enhances their status.

Height, Weight and Strength:
The Benchmarks of Change

Height reaches a maximum during the 20s for most people, and remains stable til about age 55.

After age 55, bones become less dense and ultimately women lose 2 inches and men lose 1 inch in height.

Women are more prone to declining height due to OSTEOPOROSIS, a condition in which the bones become brittle, fragile, and thin due to a lack of calcium in the body.

Height, Weight, and Strength (continued)

Both men and women continue to gain weight in middle adulthood.

The amount of body fat increases.

Exercise and weight control can ameliorate the weight gain.

Throughout middle adulthood, strength gradually decreases.

This is particularly so in the back and leg muscles.

By age 60, people have lost about 10 percent of their maximum strength.

The Senses:
The Sights & Sounds of Middle Age

Starting at age 40, visual acuity - the ability to discern fine spatial detail in both close and distant objects - begins to decline.

The eye's lenses change shape and elasticity.

The lenses become less transparent, which reduces the amount of light entering.

A nearly universal change in eyesight during middle adulthood is the loss of near vision, called PRESBYOPIA.
.
MNEMONICS are formal strategies for organizing material in ways that make it more likely to be remembered. Some suggestions
:
Get organized.

Pay attention.

Use the encoding specificity phenomenon.

Visualize.

Rehearse.

# data[].attributes.attachment_link.title
Chapter 15 Physical and Cognitive Development in Middle Adulthood

# data[].attributes.attachment_link.description
Chapter 15 Physical and Cognitive Development in Middle Adulthood Physical Development in Middle Adulthood Middle adulthood is the time when most people first become aware of the gradual changes in their bodies that mark the aging process. Declines also occur in depth perception, distance perception, the ability to view the world in three dimensions, and night vision.

# data[].attributes.attachment_link.readable_text
Brain aging is inevitable to some extent, but not uniform; it affects everyone, or every brain, differently. Slowing down brain aging or stopping it altogether would be the ultimate elixir to achieve eternal youth. Is brain aging a slippery slope that we need to accept? Or are there steps we can take to reduce the rate of decline?

Brain aging is experienced by everyone differently. The rate of cognitive decline affects some people more than others.
At around 3 pounds in weight, the human brain is a staggering feat of engineering with around 100 billion neurons interconnected via trillions of synapses.

Throughout our lifetime our brain changes more than any other part of our body. From the moment the brain begins to develop in the third week of gestation to old age, its complex structures and functions are changing, networks and pathways connecting and severing.

During the first few years of life, a child's brain forms more than 1 million new neural connections every second. The size of the brain increases fourfold in the preschool period and by age 6 reaches around 90 percent of adult volume.

The frontal lobes - the area of the brain responsible for executive functions, such as planning, working memory, and impulse control - are among the last areas of the brain to mature, and they may not be fully developed until 35 years of age.

Normal brain aging

As we age, all our body systems gradually decline - including the brain. "Slips of the mind" are associated with getting older. People often experienced those same slight memory lapses in their 20s and yet did not give it a second thought.

Having slight memory slips is normal in both younger and older people.
Older individuals often become anxious about memory slips due to the link between impaired memory and Alzheimer's disease. However, Alzheimer's and other dementias are not a part of the normal aging process.

Common memory changes that are associated with normal aging include:

Difficulty learning something new: Committing new information to memory can take longer.

Multitasking: Slowed processing can make processing and planning parallel tasks more difficult.

Recalling names and numbers: Strategic memory that helps memory of names and numbers begins to decline at age 20.

Remembering appointments: Without cues to recall the information, appointments can be put safely in storage and then not accessed unless the memory is jogged.

While some studies show that one third of older people struggle with declarative memory (memories of facts or events that have been stored and can be retrieved), other studies indicate that one fifth of 70-year-olds perform cognitive tests just as well as their 20-year-old counterparts.

Scientists are currently piecing together sections of the giant puzzle of brain research to determine how the brain subtly alters over time to cause these changes.

General changes that are thought to occur during brain aging include:

Brain mass: Shrinkage in the frontal lobe and hippocampus - areas involved in higher cognitive function and encoding new memories - starting around the age of 60 or 70 years.

Cortical density: Thinning of the outer-ridged surface of the brain due to declining synaptic connections. Fewer connections may contribute to slower cognitive processing.

White matter: White matter consists of myelinated nerve fibers that are bundled into tracts and carry nerve signals between brains cells. Myelin is thought to shrink with age, and as a result, slow processing and reduce cognitive function.

Neurotransmitter systems: Researchers suggest that the brain generates less chemical messengers with aging, and it is this decrease in dopamine, acetylcholine, serotonin, and norepinephrine activity that may play a role in declining cognition and memory and increased depression.

In understanding the neural basis of cognitive decline, researchers can uncover which therapies or strategies may help slow or prevent brain deterioration.

Recent discoveries in brain aging

Several brain studies are ongoing to solve the brain-aging conundrum, and discoveries are being frequently made.

Stem cells

Recently, researchers from Albert Einstein College of Medicine in New York revealed in a mouse study that stem cells in the brain's hypothalamus likely control how fast aging occurs in the body.

"Our research shows that the number of hypothalamic neural stem cells naturally declines over the life of the animal, and this decline accelerates aging," says Dr. Dongsheng Cai, Ph.D., professor of molecular pharmacology at Einstein. "But we also found that the effects of this loss are not irreversible. By replenishing these stem cells or the molecules they produce, it's possible to slow and even reverse various aspects of aging throughout the body."

Injecting hypothalamic stem cells into the brains of normal old mice and middle-aged mice, whose stem cells had been destroyed, slowed or reversed measures of aging. The researchers say this is a first step toward slowing the aging process and potentially treated age-related diseases.

SuperAgers

SuperAgers' brains shrink at a slower rate than people of the same age.
"SuperAgers" are a rare group of individuals over the age of 80 years who have memories as sharp as healthy people decades younger.

Research by Northwestern University Feinberg School of Medicine in Chicago, IL, compared SuperAgers with a control group of same-age individuals. They found that the brains of SuperAgers shrink at a slower rate than their age-matched peers, which results in a greater resistance to the typical memory loss observed with age, thus revealing that age-related cognitive decline is not inevitable.

"We found that SuperAgers are resistant to the normal rate of decline that we see in average elderly, and they're managing to strike a balance between life span and health span, really living well and enjoying their later years of life," says Emily Rogalski, associate professor at the Cognitive Neurology and Alzheimer's Disease Center (CNADC) at Northwestern University Feinberg School of Medicine.

By studying how SuperAgers are unique, the researchers hope to unearth biological factors that might contribute to maintaining memory ability in advanced age.

Engaging in regular exercise may help prevent cognitive and memory decline.
Therapies to help slow brain aging

Factors have been discovered that speed up brain aging. For example, obesity in midlife may accelerate brain aging by around 10 years, and both sugar and diet varieties of soda are correlated with fast-tracking brain age, having smaller overall brain volume, poorer episodic memory, and a shrunken hippocampus.

A growing body of evidence suggests that people who experience the least declines in cognition and memory all share certain characteristics:

partaking in regular physical activity

pursuing intellectually stimulating activities

staying socially active

managing stress

eating healthily

sleeping well

Recent research highlights a plethora of ways that we can actively take charge of our health and perhaps decrease the rate at which our brains age.

Exercise

One intervention that crops up time and time again to stave off age-related mental decline is exercise.

A combination of aerobic and resistance exercise of moderate intensity for at least 45 minutes each session and on as many days of the week as possible has been reported to boost brain power in people aged 50 and over significantly.

Likewise, other research by the University of Miami found that individuals over the age of 50 who engaged in little to no exercise experienced a decline in memory and thinking skills comparable to 10 years of aging in 5 years, compared with those who took part in moderate- or high-intensity exercise. Essentially, physical activity slowed brain aging by 10 years.

Playing a musical instrument may help prevent some of the cognitive decline that accompanies aging.
Dancing has also shown to have an anti-aging effect on the brain of seniors. A study conducted by the German Center for Neurodegenerative Diseases, Magdeburg, Germany found that while regular exercise can reverse the signs of brain aging, the most profound effect was seen in people who danced.

Playing an instrument

Baycrest Health Sciences in Toronto, Canada, revealed why playing a musical instrument may help older adults ward off age-related cognitive declines and retain their listening skills.

Researchers found that learning to play a sound on a musical instrument changes brain waves in such a way that improves an individual's listening and hearing skills. The alteration in brain activity indicates that the brain rewires itself to compensate for disease or injuries that might prevent a person's ability to perform tasks.

"It has been hypothesized that the act of playing music requires many brain systems to work together, such as the hearing, motor and perception systems," said Dr. Bernhard Ross, senior scientist at Baycrest's Rotman Research Institute. "This study was the first time we saw direct changes in the brain after one session, demonstrating that the action of creating music leads to a strong change in brain activity."

Diet

A key component of brain health is diet. Recent research has linked omega-3 and omega-6 fatty acids in the blood with healthy brain aging. Another study has also determined that consuming foods included in the Mediterranean or the MIND diet is associated with a lower risk of memory difficulties in older adults.

Research by the University of Illinois, Champaign, IL, discovered that middle-aged people who have higher levels of lutein - a nutrient that is found in green leafy vegetables, such as kale and spinach, and eggs and avocados - had similar neural responses to younger individuals than of people the same age.

"As people get older, they experience typical decline. However, research has shown that this process can start earlier than expected. You can even start to see some differences in the 30s," informs Anne Walk, a postdoctoral scholar and the first author of the study. "We want to understand how diet impacts cognition throughout the lifespan. If lutein can protect against decline, we should encourage people to consume lutein-rich foods at a point in their lives when it has maximum benefit."

The number of American adults over the age of 65 is set to more than double in 40 years, rising from 40.2 million in 2010 to 88.7 million by the year 2050. Due to this aging population, it will become increasingly important to understand the cognitive changes that go hand in hand with aging.

While many questions remain regarding the aging brain, research is making progress in illuminating what happens to our cognitive functions and memory throughout our lifetime, and it is emphasizing ways we can preserve our mental abilities to improve our quality of life as we advance into older adulthood.

# data[].attributes.attachment_link.description
Brain aging is inevitable to some extent, but not uniform; it affects everyone, or every brain, differently. Slowing down brain aging or stopping it altogether would be the ultimate elixir to achieve eternal youth. Is brain aging a slippery slope that we need to accept?

# data[].attributes.attachment_link.readable_text
Like the rest of your body, your brain changes with each passing year. From the time we are infants, our brains are adapting, learning, making memories and more. We become smarter and sharper, earning the wisdom that truly only comes with life experience. The less desirable effects of the march of time can certainly be felt, too. You may recognize them: An ever-lost set of keys, a to-do that never seems to stay top of mind, a name that's on the tip of your tongue.

Once we hit our late twenties, the brain's aging process begins and we begin losing neurons-the cells that make up the brain and nervous system. By our sixties, our brains have literally begun to shrink. Though these brain changes may sound a bit scary, the process is natural and it happens to everyone.

Learn how your brain changes as you age to get a better handle on what is happening in this magical part of your body. Then, review some of the things that you can do to help preserve brain health. Though some change is inevitable, some can be warded off with a healthy lifestyle. Here's how you can take an active role in slowing negative effects and working to stay sharper, longer.

Birth to Toddler Years
You are born with basic survival skills, reflexes and most of the 100 billion neurons that you'll have for the duration of your life. The brain grows incredibly rapidly during these early years: Neurons get bigger, work more efficiently and-as a result of environmental input and stimuli-make trillions of connections that fine-tune everything from hearing to vision. By two years old, your brain is about 80 percent of its adult size.

Early to Middle Childhood
About 85 percent of brain development has occurred by now, including intellect, personality and motor and social skills. A child's brain has twice as many synapses as an adult's brain. In a process called pruning, the neural connections that are used and reinforced most often-like those used for language-are strengthened, while the ones that are not utilized as much fizzle and die. (That's why parents are often encouraged to repeat certain activities, like reading books, with their kids every day.)

Teens
At this point the brain reaches its adult weight of about three pounds. Increased activity in the frontal lobes allows a teenager to compare several concepts at once.

20s
The regions in the frontal lobe that are responsible for judgment, planning, weighing risks and decision-making finally finish developing. A twenty-something's brain has reached its peak in terms of performance.

Late 20s to Early 30s
Reasoning, spatial skills and speed of thought begin to decline around now. As you age, your brain goes through changes that can slow down your thinking: It loses volume, the cortex becomes thinner, the myelin sheath surrounding the fibers of your neurons begins to degrade, and your brain receptors don't fire as quickly.

Mid 30s
What was that woman's name, again? In your 30s, memory begins to slip as the number of neurons in the brain decreases. It may take longer to learn new things or memorize words or names. This process continues in the decades ahead.

40s and 50s
From your mid 40s to late 50s, your reasoning skills slow. In a group of people who were first tested on various mental abilities when they were 45-49 years old, reasoning skills declined by 3.6 percent over 10 years, according to research in the British Medical Journal. The middle-age participants also experienced fading sharpness in memory and verbal fluency-the ability to say words quickly in a specific category. On the upside, other measures of cognition-such as moral decision-making, regulating emotions and reading social situations-have been shown to improve beginning with middle age. Experts suspect that simply living life and gaining experience deserves some of the credit. (Bonus fact: Starting at around age 40, people tend to remember positive images more than negative ones-a trend that continues until at least age 80.)

60s
The brain has begun to shrink in size and, after a lifetime of gaining accumulated knowledge, it becomes less efficient at accessing that knowledge and adding to it. The greatest risk factor for Alzheimer's is advancing age, and most individuals with the disease are 65 or older. Surprisingly, when Alzheimer's hits people in their 60s and 70s, they show faster rates of brain tissue loss and cognitive decline compared to patients 80 years and older, according to researchers at the University of California, San Diego School of Medicine. Researchers aren't sure why Alzheimer's is more aggressive in younger patients, but suspect that people who develop symptoms later in life may have milder cases-or cases that that take longer to reveal themselves.

70s and 80s
Your risk of developing Alzheimer's increases with age, reaching 50 percent by age 85. Researchers aren't sure why the risk jumps so dramatically as we get older, but it's possible the disease is linked to inflammation, a natural part of aging that can lead to a build-up of deposits in areas like the hippocampus, the part of the brain responsible for forming new memories. These deposits may also interfere with long-term memory. Along with aging, many experts think that genes and lifestyle contribute to the majority of Alzheimer's and dementia cases.
Proven Brain Boosters
Even the healthiest among us cannot stop our brains from changing with time. That being said, certain behaviors can help your brain stay as sharp as possible:

Break a Sweat. Exercise pumps blood to the brain and encourages the growth of new brain cells-and you don't have to spend hours at the gym to get the positive effects. Research shows that regular aerobic exercise, like walking or cycling, for 30 minutes a day reduces brain cell loss. (Regular physical activity can also significantly reduce the risk of heart attack, stroke, diabetes and more.)

Challenge Yourself. Studies show that mentally stimulating activities may help reverse cognitive decline. Just as lifting dumbbells strengthens your muscles, keeping your mind engaged seems to increase the brain's vitality and may build its reserves of brain cells and connections. Do stimulating activities that you enjoy: Read, write, put together a jigsaw puzzle, work on crosswords...it all counts.

Listen to Music. A study in the journal Neuron showed that listening to music may sharpen the brain's ability to anticipate events and stay focused. Researchers took an MRI of people's brains while they were listening to symphony music, and then when they weren't. When music played, the areas of the brain involved with paying attention, making predictions and accessing memories were engaged; the same couldn't be said when it was quiet.

Nurture Your Relationships. Invest in your bonds with friends and loved ones. Experts suspect that social interaction requires you to engage the areas of the brain involved in memory and attention, the same mental processes that are used in many cognitive tasks. Furthermore, one study revealed that activities that combine social interaction with physical and mental activity may help prevent dementia. Sign up for a dance class, which allows you to spend time with pals, get moving and challenge your brain as it works to keep up with all those tricky steps.

Eat Wisely. Certain foods are rich in vitamins and other nutrients that can help thwart threats to your brain health. For example, regularly eating vibrantly-hued fruits and vegetables, which have high levels of disease-fighting antioxidants, will help counteract disease-causing free radicals throughout the body, including the brain. Cook meals with ingredients containing mono- and polyunsaturated fats, which can improve levels of HDL ("good") cholesterol and-according to research-may help protect brain cells.

Drink in Moderation. While we do not recommend taking up drinking alcoholic beverages, you might be surprised to learn that drinking alcohol sparingly may be beneficial to your brain. At least five studies have linked low-dose alcohol consumption-a drink a day for women, two for men-with a reduced risk of dementia in older adults. Be careful not to go outside those limits: Heavy alcohol use has been linked to an increased risk of dementia and cognitive decline, among other health concerns.

Stay Smoke-Free. Smoking can affect your body's ability to deliver to the brain oxygen and nutrients that help keep it healthy, and some studies have indicated that it can even speed up the brain's natural aging process. Smoking can also lead to the formulation of plaques that can contribute to dementia.

Protect Your Head. Experts think that there may be a connection between serious head injury and Alzheimer's disease, especially when trauma occurs repeatedly or involves loss of consciousness. Protect your brain by wearing a seatbelt, using a helmet when participating in sports and fall-proofing your home.

# data[].attributes.attachment_link.description
Like the rest of your body, your brain changes with each passing year. From the time we are infants, our brains are adapting, learning, making memories and more. We become smarter and sharper, earning the wisdom that truly only comes with life experience. The less desirable effects of the march of time can certainly be felt, too.

# data[].attributes.attachment_link.readable_text
Abstract

Ageing causes changes to the brain size, vasculature, and cognition. The brain shrinks with increasing age and there are changes at all levels from molecules to morphology. Incidence of stroke, white matter lesions, and dementia also rise with age, as does level of memory impairment and there are changes in levels of neurotransmitters and hormones. Protective factors that reduce cardiovascular risk, namely regular exercise, a healthy diet, and low to moderate alcohol intake, seem to aid the ageing brain as does increased cognitive effort in the form of education or occupational attainment. A healthy life both physically and mentally may be the best defence against the changes of an ageing brain. Additional measures to prevent cardiovascular disease may also be important.

Keywords: ageing, brain, cognition

The effects of ageing on the brain and cognition are widespread and have multiple aetiologies. Ageing has its effects on the molecules, cells, vasculature, gross morphology, and cognition. As we age our brains shrink in volume, particularly in the frontal cortex. As our vasculature ages and our blood pressure rises the possibility of stroke and ischaemia increases and our white matter develops lesions. Memory decline also occurs with ageing and brain activation becomes more bilateral for memory tasks. This may be an attempt to compensate and recruit additional networks or because specific areas are no longer easily accessed. Genetics, neurotransmitters, hormones, and experience all have a part to play in brain ageing. But, it is not all negative, higher levels of education or occupational attainment may act as a protective factor. Also protective are a healthy diet, low to moderate alcohol intake, and regular exercise. Biological ageing is not tied absolutely to chronological ageing and it may be possible to slow biological ageing and even reduce the possibility of suffering from age related diseases such as dementia.

Physical changes

Cognitive change

The most widely seen cognitive change associated with ageing is that of memory. Memory function can be broadly divided into four sections, episodic memory, semantic memory, procedural memory, and working memory.18 The first two of these are most important with regard to ageing. Episodic memory is defined as "a form of memory in which information is stored with 'mental tags', about where, when and how the information was picked up".19 An example of an episodic memory would be a memory of your first day at school, the important meeting you attended last week, or the lesson where you learnt that Paris is the capital of France. Episodic memory performance is thought to decline from middle age onwards. This is particularly true for recall in normal ageing and less so for recognition.20 It is also a characteristic of the memory loss seen in Alzheimer's disease (AD).18

Semantic memory is defined as "memory for meanings", for example, knowing that Paris is the capital of France, that 10 millimetres make up a centimetre, or that Mozart composed the Magic Flute.19 Semantic memory increases gradually from middle age to the young elderly but then declines in the very elderly.20 It is not yet clear why these changes occur and it has been hypothesised that the very elderly have less resources to draw on and that their performance may be affected in some tasks by slower reaction times, lower attentional levels, slower processing speeds, detriments in sensory and or perceptual functions, or potentially a lesser ability to use strategies.20,21,22,23

There have been studies investigating different types of memory in ageing using neuropsychological testing and neuroimaging. However, it must be pointed out that it is sometimes methodologically difficult to separate some of these functions, for example episodic memory encoding and semantic memory retrieval.24 Despite this studies are beginning to examine performance on memory tasks with ageing and by neuroimaging. A review article focusing in this area highlighted the changes in regional brain activation.24 Older brains tend to show more symmetrical activation, either because they have increased activation in a hemisphere that is less activated than in younger adults or because they show reduced activation in the areas most activated in younger adults. This has been shown for visual perception and in memory tasks.24 The observed changes in activation in the left and right prefrontal cortex are in keeping with changes in memory performance, particularly episodic memory, as this is thought to be based in this area.24 It has also been suggested that the actual level of brain activation, as shown in neuroimaging, may be related more directly to the levels of memory performance.25 A review of studies using electroencephalograms to examine event related potentials in response to stimuli also contribute some support for increased symmetry in brain activation with age.26

The increased symmetrical hemispheric activation is a robust finding and has been referred to as HAROLD or hemispheric asymmetry reduction in older adults. It is not clear whether this change is an attenuation of the response seen in younger subjects, an inability to recruit specific areas, or an attempt to compensate for the ageing process.21,23,25 This change in activation occurring in the frontal lobes fits with changes in memory performance and with the possible white matter changes referred to above, however, other factors such as changes in neurotransmitter or hormone levels also require consideration.

Mechanisms of change

Another factor to consider with regard to the ageing brain and its cognitive performance is hormonal influence. It is known that sex hormones can affect cognitive processes in adulthood and that changes in sex hormones occur in ageing particularly in women at menopause. Women also have a higher incidence of AD even when longer life expectancy is taken into account.14 AD is characterised by failing memory and there has been a suggestion that oestrogen therapy may increase dopaminergic responsivity32 and play a protective part in AD.33,34 It must be remembered though that the use of HRT has recently been shown to have cancer risks.35 Growth hormone levels also decline with age and may be associated with cognitive performance although the evidence is far from clear.36

The ageing brain may also suffer from impaired glucose metabolism20 or a reduced input of glucose or oxygen as cerebrovascular efficiency falls, although reduction in glucose may partly be attributable to atrophy rather than any change in glucose metabolism.37 Change in vasculature is important and another common finding in elderly brains related to ischaemia are white matter lesions and stroke.

Vascular factors and dementia

Increasing evidence points to vascular factors not only contributing to cognitive problems in ageing but also to the two most common dementias seen in this population. The prevalence of dementia increases almost exponentially with increasing age with around 20% of those aged 80 affected rising to 40% of those aged 90.39

Protective factors

Conclusion

That the brain changes with increasing chronological age is clear, however, less clear is the rate of change, the biological age of the brain, and the processes involved. The brain changes that may affect cognition and behaviour occur at the levels of molecular ageing, intercellular and intracellular ageing, tissue ageing, and organ change. There are many areas of research under investigation to elucidate the mechanisms of ageing and to try to alleviate age associated disorders, particularly dementias that have the biggest impact on the population. In terms of personal brain ageing the studies suggest that a healthy lifestyle that reduces cardiovascular risk will also benefit the brain. Medical care in this area may even offer limited protection in terms of cognitive decline but this needs to be shown for antihypertensives, antiplatelet, and anticholesterol agents. It is also important to take note of the limitations in studies on the ageing brain. Many studies are cross sectional in nature, have small numbers of participants with wide ranges in chronological age, lack control for risk factors or protective factors, take no account of education that may improve performance on cognitive tests, and finally lack assessment with regard to depression that may also affect performance. It must be remembered that the brains of an elderly group may show cohort effects related to wider environmental influences, for example, lack of high energy foods while growing up.2 It is also extremely difficult to separate out and measure single cognitive processes to fully understand any changes.106

Future studies need to take full account of these factors and "cross sequential", a combination of cross sectional and longitudinal studies, have been proposed.3 It is clear that our understanding of the ageing brain continues to grow but still requires much research that is especially important given the numbers of elderly people in society and their potential levels of cognitive impairment. Where appropriate, randomised controlled trials of therapeutic measures may, in future, lead the way to greater understanding.

Abbreviations

AD - Alzheimer's disease

WML - white matter lesion

VaD - vascular dementia

Footnotes

Funding: none.

Conflicts of interest: none.

References

3. Raz N. The ageing brain: structural changes and their implications for cognitive ageing. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 2004115-134.

9. Levine B, Cabeza R, McIntosh A.[[ et al Functional reorganisation of memory after traumatic brain injury: a study with H ₂ ¹⁵O positron emission tomography. J Neurol Neurosurg Psychiatry 200273173-181. PubMed] PMC free article] [ Google Scholar]

11. Tullberg M, Fletcher E, DeCarli C.[[ et al White matter lesions impair frontal lobe function regardless of their location. Neurology 200463246-253. PubMed] PMC free article] [ Google Scholar]

13. Artero S, Tiemeier H, Prins N.[[ et al Neuroanatomical localisation and clinical correlates of white matter lesions in the elderly. J Neurol Neurosurg Psychiatry 2004751304-1308. PubMed] PMC free article] [ Google Scholar]

15. Hultsch D, Macdonald S. Intraindividual variability in performance as a theoretical window onto cognitive ageing. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 200465-88.

18. Parkin A.Memory and amnesia. Oxford: Blackwall, 1997

19. Reber A S.Dictionary of psychology. London: Penguin, 1995

20. Nyberg L, Bäckman L. Cognitive ageing: a view from brain imaging. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 2004135-160.

21. Cabeza R. Commentary: neuroscience frontiers of cognitive ageing: approaches to cognitive neuroscience of ageing. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 2004179-198.

27. Mukherjee J, Christian B, Dunigan K.[ et al Brain imageing of ¹⁸F‐Fallypride in normal volunteers: blood analysis, distribution, test‐retest studies, and preliminary assessment of sensitivity to ageing effects on dopamine D‐2/D‐3 receptors. Synapse 200246170-188. [ PubMed] Google Scholar]

30. Toescu E, Verkhratsky A, Landfield P. Ca[ ²⁺ regulation and gene expression in normal brain ageing. Trends Neurosci 200427614-620. [ PubMed] Google Scholar]

33. Herlitz A, Yonker J. Hormonal effects on cognition in adults. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 2004253-278.

35. Ng C, Panay N. Hormone replacement therapy update. Geriatric Medicine 20043427-34. [ Google Scholar]

59. Blauw G, Bollen E, Buchem M. et al Dementia at old age: a clinical end‐point of atherosclerotic disease. Eur Heart J 2001(suppl 3)N16-N19. [ PubMed]

75. Arneiz E, Almkvist O, Ivnik R.[[ et al Mild cognitive impairment: a cross‐national comparison. J Neurol Neurosurg Psychiatry 2003751275-1280. PubMed] PMC free article] [ Google Scholar]

80. Shepherd J, Blauw G, Murphy M, on behalf of the PROSPER study group et al Pravastatin in elderly individuals at risk of vascular disease (PROSPER): a randomised controlled trial. Lancet 20021-8. [ PubMed]

83. Sastre A, Grimley Evan J. Effect of the treatment of type II diabetes mellitus on the development of cognitive impairment and dementia. Cochrane Library. Issue 2. Oxford: Update Software, 2003

106. Hertzog C. Does longitudinal evidence confirm theories of cognitive ageing derived from cross‐sectional data? In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 200441-64.

Articles from Postgraduate Medical Journal are provided here courtesy of BMJ Publishing Group

# data[].attributes.attachment_link.description
Ageing causes changes to the brain size, vasculature, and cognition. The brain shrinks with increasing age and there are changes at all levels from molecules to morphology. Incidence of stroke, white matter lesions, and dementia also rise with age, as ...