Our physical maturation is complete by the time we reach early adulthood, though our height and weight can increase slightly. Our physical abilities, such as muscle strength, response speed, sensory abilities, and cardiac functioning, are at their highest in early adulthood. During this time, most professional athletes are at the top of their game, and many women have children in their early adult years.

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

Young adults need to form intimate, loving relationships with other people. Success leads to strong relationships, while failure results in loneliness and isolation. This stage covers the period of early adulthood when people are exploring personal relationships. Erikson believed it was vital that people develop close, committed relationships with other people. Those who are successful at this step will form relationships that are enduring and secure.

The aging process becomes more visible during middle adulthood. Presbyopia is a condition in which the eyes lose their ability to respond to stimuli at different distances about the age of 60. The majority of people between the ages of 40 and 60 will need corrective lenses to correct vision issues. Certain eye disorders, such as glaucoma, are more common in middle-aged adults than in younger adults. Hearing continues to deteriorate: 14% of middle-aged Americans have hearing loss. Skin continues to dry out, making it more vulnerable to wrinkles, particularly on the delicate face region. When the skin dries out and thins, age spots and blood vessels become more visible. 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.

The key focus of middle adulthood is on two types of intelligence: crystallized and fluid intelligence. Our crystallized wisdom is built on a foundation of cumulative knowledge and experience—the knowledge, skills, and techniques we've acquired over the course of our lives. As we get older, this type of intelligence continues to stay the same or even strengthen. Adults, for example, have relatively stable to rising intelligence test scores until their mid-30s to mid-50s (Bayley & Oden, 1955). Fluid intelligence, on the other hand, is more reliant on basic information-processing abilities and begins to deteriorate long before reaching middle age. 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.

Adults need to create or nurture things that will outlast them, often by having children or creating a positive change that benefits other people. Success leads to feelings of usefulness and accomplishment, while failure results in shallow involvement in the world. During adulthood, we continue to build our lives, focusing on our career and family. Those who are successful during this phase will feel that they are contributing to the world by being active in their home and community. Those who fail to attain this skill will feel unproductive and uninvolved in the world.

During late adulthood the skin continues to lose elasticity, reaction time slows further, muscle strength and mobility diminishes, hearing and vision decline, and the immune system weakens. Memory degenerates in old age, so older adults have a harder time remembering and attending to information. In general, an older person’s procedural memory tends to remain stable, while working memory declines.

During old age, a general decline in memory is very common, due to the decrease in speed of encoding, storage, and retrieval of memory. Neurocognitive disorder, formerly called dementia, is a broad category of brain diseases that cause a gradual long-term decrease in the ability to think and remember. There is no cure for neurocognitive disorder, but there are many strategies to improve quality of life for people with this disorder, such as daily exercise programs and cognitive or behavioral therapies.

At this point in development, people look back on the events of their lives and determine if they are happy with the life that they lived or if they regret the things they did or didn't do.
Erikson's theory differed from many others because it addressed development throughout the entire lifespan, including old age. Older adults need to look back on life and feel a sense of fulfillment. Success at this stage leads to feelings of wisdom, while failure results in regret, bitterness, and despair.
At this stage, people reflect back on the events of their lives and take stock. Those who look back on a life they feel was well-lived will feel satisfied and ready to face the end of their lives with a sense of peace. Those who look back and only feel regret will instead feel fearful that their lives will end without accomplishing the things they feel they should have.​