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One example of when senses interact in your daily life is the connection between taste and sight. Particularly with drinks, the vibrancy of a drink dictates how strong of a flavor we believe is present. For example, if I were given two cups of hot chocolate, one being a watery brown, and the other one being a dark, rich brown, I would be more likely to think that the darker sample tastes stronger, even if the two taste exactly the same in reality. The extreme color saturation increases perceived flavor intensity in taste.

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Directions-  How do YOUR senses interact?

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Directions-  How do YOUR senses interact?

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Now it is time for you to share how your senses interact!

The following pages provide space for you to answer the two questions posed.

1. Provide an example in your life where two or more of your senses have worked together to set the scene for you.

2. Do you think you have any Synesthete tendencies? If so, what are they? If not, which Synesthete tendency do you find most fascinating?

Each student will have their own post  to enter their responses. Please feel free to use the links given on the next page to help in your research. .

Afterwards, you may look at what other classmates said and respond/comment on TWO posts! Did you find any similarities? Did they make a point about sensory interaction that you did not consider? Did they find a neat synesthete tendency that you had not come across?

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The only Synesthete tendency I partially demonstrate is personification. This type is called ordinal-linguistic personification, or OLP for short. I do not engage in this personification naturally (at least not casually/consistently), but if I were given the task to personify a certain inanimate object or quality, I could come to a definitive conclusion somewhat quickly. I mean this in the sense that it would not take much deliberation or debate, and I would be somewhat stubborn and definitie in my personification route. Additionally, although I do not practice this personification all of the time, there are a few letters and numbers that I have always associated a quality with. For example, I have always thought that the number 8 was gentle and nice, which is part of the reason why it is my favorite single digit number.

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Synesthesia Discussion Board SlideDeck - Resources

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Synesthesia Discussion Board SlideDeck - Resources

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The smell of the ocean, the sight of the beach and the sound of the waves.

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One example of senses interacting in your daily life is sight and sound. When you look at something you automatically assume the sound they would make. This can be true for looking at a tea kettle. When you look at a tea kettle you can almost hear the whistling sound that it makes even if its not on.

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I once heard the sound of the waves and thought of the color pastel blue. Another example is me associating the word relax with forest green

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No, but I think relating numbers with colors is interesting.

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One example of two senses impact your daily life is sight and taste, if an item of food doesnt look good you probably won't want to taste it. But if the food looks good you will want to taste it.

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One example in my life when senses interacted with each other was when I was at disney and I saw a cinnamon roll and so I remembered what it taste like and could taste it in my mouth even though it wasn't' really there.

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One example of when senses worked together in my life is when I smell something specific and then it brings me back to a certain memory that I have and then any dialogue or music during that time would repeat in my head.

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An example in my life where two or more senses work together is through my sense of sight and smell. Often when I see an aromatic food or drink, no matter how far away it is or whether it's on the other side of a window, I can smell and sometimes even taste it (given that I've tasted or smelt it before).

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One example of when senses have interacted in my daily life is with sight and taste. I tend to associate colors with different flavors. For example, if I eat a purple candy I will usually associate it with grape flavor even if it actually isn't flavored and would be more steered away from eating it sense I am not a big fan of grape flavor.

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I don't have any synesthete tendencies but I find it really fascinating when people with synesthesia can see certain colors when they hear people's names.

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I haven't been able to recognize many synesthesia tendencies that I may have, but one that I have been able to identify is similar to the student example. Sometimes I can personify or identify specific objects or numbers with certain personality traits and characteristics, similar to what we talked about in class when we applied different colors to different subjects in school. Example - Science = Green, History = Orange.

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When I saw a cheese burger on Instagram and knew the taste of it without having a bite

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Sense and sense abilities: How synesthesia changes what people experience

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Synesthesia is experiencing a sensory crossover, like tasting sounds or hearing colors. It's not a medical condition, but it is sometimes a symptom of certain issues.

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The synesthete that I find most fascinating is the ones that use music as an association.

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I think smell and taste really work well together because sometimes the smell of something is the same as it tastes or even makes it taste better because the smell is so good.

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When I am eating candy I choose the orange colored one of that candy, even if they all taste the same. This is because I prefer the orange color

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No I do not have any tendencies but one I think is very intriguing is matching colors with words or numbers.

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I don't think that I have any sort of Synesthete tendencies, but what I find most interesting and fascinating is the association of numbers or letters with different tastes.

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Hearing Colors, Seeing Sounds: Synesthesia

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I don't believe I have any synthetic tendencies but I think the idea of associating a word to a taste is quite interesting.

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When you use both taste and smell to identify a certain type of food.

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I don't think I have any synesthete tendencies, but Lexical-Gustatory synesthesia is very interesting.

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I find being able to taste a name to be the most interesting to me.

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I tend to associate numbers and letters with colors. I do not believe I have real synesthesia, but make associations between things a lot.

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https://synthesiagame.com/

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No, however I find it very fascinating that some people can taste things like name's and how this affects what they think of that person.

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Synesthesia is a neurological condition in which stimulation of one sensory or cognitive pathway (for example, hearing) leads to automatic, involuntary experiences in a second sensory or cognitive pathway (such as vision). Simply put, when one sense is activated, another unrelated sense is activated at the same time. This may, for instance, take the form of hearing music and simultaneously sensing the sound as swirls or patterns of color.

Understanding Synesthesia

Sight, smell, taste, touch, sound... and synesthesia? Though we're no closer to discovering a true sixth sense, research suggests that synesthesia may confer some sensory enhancements. Some scientists posit, for example, that synesthetes are better at distinguishing between smells as well as between colors.

Synesthesia can enhance cognitive abilities such as creativity and memory, as it's easier to make connections between concepts. Renowned creative minds such as Vincent Van Gogh and Vladimir Nabokov claimed to have synesthesia.

Synesthesia can be associative, so senses are connected and associated in a person's mind, or projective, when the images and colors are projected into reality.

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The Different Types of Synesthesia

Since synesthesia can involve any combination of the senses, there may be as many as 60 to 80 subtypes. However, not all types of synesthesia have been documented or studied, and the cause remains unclear. Some synesthetes perceive texture in response to sight, hear sounds in response to smells, or associate shapes with flavors. Media like books, films, and TV shows often take advantage of the multimodal mental imagery associated with synesthesia (which explains the popularity of cooking and baking shows).

While nearly any sensory combination is possible in synesthesia, here are some of the most well-known ways it manifests:

Auditory-tactile synesthesia occurs when a sound prompts a specific bodily sensation (such as tingling on the back of one's neck).

Chromesthesia occurs when certain sounds (like a car honking) can trigger someone to see colors.

Grapheme-color synesthesia occurs when letters and numbers are associated with specific colors.

Lexical-gustatory synesthesia occurs when hearing certain words triggers distinct tastes.

Mirror-touch synesthesia has been described as a kind of supercharged empathy: A person feels as though they're being touched if they witness it happening to someone else. It can be benign-such as an observed advantage in recognizing facial expressions-or burdensome, as in the case of a neurologist who felt intense pressure in his chest when he saw a patient receiving CPR.

Number form occurs whena mental map of numbers involuntarily appears whenever someone thinks of numbers.

Ordinal linguistic personification is a kind of synesthesia where ordered sequences (e.g., the days of the week) are associated with personalities or genders.

Spatial sequence synesthesia involves seeing numbers or numerical sequences as points in space (e.g., close or far away).

Do You Have Synesthesia?

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Synesthesia is a neurological condition in which stimulation of one sensory or cognitive pathway (for example, hearing) leads to automatic, involuntary experiences in a second sensory or cognitive pathway (such as vision). Simply put, when one sense is activated, another unrelated sense is activated at the same time.

# data[].attributes.attachment_link.readable_text
Synesthesia is a neurological condition in which stimulation of one sensory or cognitive pathway (for example, hearing) leads to automatic, involuntary experiences in a second sensory or cognitive pathway (such as vision). Simply put, when one sense is activated, another unrelated sense is activated at the same time. This may, for instance, take the form of hearing music and simultaneously sensing the sound as swirls or patterns of color.

Understanding Synesthesia

Sight, smell, taste, touch, sound... and synesthesia? Though we're no closer to discovering a true sixth sense, research suggests that synesthesia may confer some sensory enhancements. Some scientists posit, for example, that synesthetes are better at distinguishing between smells as well as between colors.

Synesthesia can enhance cognitive abilities such as creativity and memory, as it's easier to make connections between concepts. Renowned creative minds such as Vincent Van Gogh and Vladimir Nabokov claimed to have synesthesia.

Synesthesia can be associative, so senses are connected and associated in a person's mind, or projective, when the images and colors are projected into reality.

article continues after advertisement

The Different Types of Synesthesia

Since synesthesia can involve any combination of the senses, there may be as many as 60 to 80 subtypes. However, not all types of synesthesia have been documented or studied, and the cause remains unclear. Some synesthetes perceive texture in response to sight, hear sounds in response to smells, or associate shapes with flavors. Media like books, films, and TV shows often take advantage of the multimodal mental imagery associated with synesthesia (which explains the popularity of cooking and baking shows).

While nearly any sensory combination is possible in synesthesia, here are some of the most well-known ways it manifests:

Auditory-tactile synesthesia occurs when a sound prompts a specific bodily sensation (such as tingling on the back of one's neck).

Chromesthesia occurs when certain sounds (like a car honking) can trigger someone to see colors.

Grapheme-color synesthesia occurs when letters and numbers are associated with specific colors.

Lexical-gustatory synesthesia occurs when hearing certain words triggers distinct tastes.

Mirror-touch synesthesia has been described as a kind of supercharged empathy: A person feels as though they're being touched if they witness it happening to someone else. It can be benign-such as an observed advantage in recognizing facial expressions-or burdensome, as in the case of a neurologist who felt intense pressure in his chest when he saw a patient receiving CPR.

Number form occurs whena mental map of numbers involuntarily appears whenever someone thinks of numbers.

Ordinal linguistic personification is a kind of synesthesia where ordered sequences (e.g., the days of the week) are associated with personalities or genders.

Spatial sequence synesthesia involves seeing numbers or numerical sequences as points in space (e.g., close or far away).

Do You Have Synesthesia?

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Synesthesia is a neurological condition in which stimulation of one sensory or cognitive pathway (for example, hearing) leads to automatic, involuntary experiences in a second sensory or cognitive pathway (such as vision). Simply put, when one sense is activated, another unrelated sense is activated at the same time.

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One example of senses interacting in your daily life, is when food at a restaurant smells and looks appetizing, I assume the food tastes good.

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Being able to kind of taste something based off the smell of it.

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What's It Like To Hear Colors? - A VR 360° Synesthesia Experience

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No but I think its cool that some people can "taste" names.

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I am not diagnosed nor do I believe I have any Synesthete tendencies. I feel as though it is just my senses working at the same time. Although I do think being able to see certain colors with numbers and being able to point it out immediately.

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When you're walking outside and you can hear the crunch of snow under your feet and the lack of leaves on the tree branches.

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When I taste a food I can sometimes see what I am eating or the packaging it comes in.

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Guitar music doesn't just tickle Carol Crane's fancy--it also brushes softly against her ankles. When she hears violins, she also feels them on her face. Trumpets make themselves known on the back of her neck.

In addition to feeling the sounds of musical instruments on her body, Crane sees letters and numbers in brilliant hues. And for her, units of time each have their own shape: She sees the months of the year as the cars on a ferris wheel, with July at the top, December at the bottom.

Sean Day, PhD, tastes in technicolor.

"The taste of beef, such as a steak, produces a rich blue," says Day, a linguistics professor at National Central University in Taiwan. "Mango sherbet appears as a wall of lime green with thin wavy strips of cherry red. Steamed gingered squid produces a large glob of bright orange foam, about four feet away, directly in front of me."

Crane and Day share an extraordinary sensory condition called synesthesia.

The phenomenon--its name derives from the Greek, meaning "to perceive together"--comes in many varieties. Some synesthetes hear, smell, taste or feel pain in color. Others taste shapes, and still others perceive written digits, letters and words in color. Some, who possess what researchers call "conceptual synesthesia," see abstract concepts, such as units of time or mathematical operations, as shapes projected either internally or in the space around them. And many synesthetes experience more than one form of the condition.

The condition is not well known, in part because many synesthetes fear ridicule for their unusual ability. Often, people with synesthesia describe having been driven to silence after being derided in childhood for describing sensory connections that they had not realized were atypical.

For scientists, synesthesia presents an intriguing problem. Studies have confirmed that the phenomenon is biological, automatic and apparently unlearned, distinct from both hallucination and metaphor. The condition runs in families and is more common among women than men, researchers now know. But until recently, researchers could only speculate about the causes of synesthesia.

Now, however, modern behavioral, brain-imaging and molecular genetic tools hold exciting promise for uncovering the mechanisms that drive synesthesia--and, researchers hope, for better understanding how the brain normally organizes perception and cognition.

Research suggests that about one in 2,000 people are synesthetes, and some experts suspect that as many as one in 300 people have some variation of the condition. The writer Vladimir Nabokov was reputedly a synesthete, as were the composer Olivier Messiaen and the physicist Richard Feynman.

The most common form of synesthesia, researchers believe, is colored hearing: sounds, music or voices seen as colors. Most synesthetes report that they see such sounds internally, in "the mind's eye." Only a minority, like Day, see visions as if projected outside the body, usually within arm's reach.

Some synesthetes report experiencing sensory overload, becoming exhausted from so much stimulation. But usually the condition is not a problem--indeed, most synesthetes treasure what they consider a bonus sense.

"If you ask synesthetes if they'd wish to be rid of it, they almost always say no," says Simon Baron-Cohen, PhD, who studies synesthesia at the University of Cambridge. "For them, it feels like that's what normal experience is like. To have that taken away would make them feel like they were being deprived of one sense."
Scientific milestones
In the late 19th and early 20th centuries, synesthesia enjoyed a flurry of scientific study, mostly descriptive. By the mid-20th century, however, synesthesia had fallen off scientists' radar, a casualty of the behaviorism movement. The phenomenon began to resurface as a subject of psychological inquiry beginning in the 1970s, stimulated largely by the work of two scientists.

In 1975, Yale University psychologist Larry Marks, PhD, authored a review of the early history of synesthesia research in the journal Psychological Bulletin (Vol. 82, No. 3), the first major psychological treatment of the subject after a 30-year drought. Then, in the early 1980s, neurologist Richard E. Cytowic, MD, published several case reports of synesthesia. He proposed, provocatively, that the condition's cause rests in the limbic system, a more emotional and "primitive" part of the brain than the neocortex, where higher order thinking occurs. Although that theory has not received widespread support, Cytowic's case studies and his popular 1993 book, "The Man Who Tasted Shapes," heightened synesthesia's prominence and prompted psychologists and neuroscientists to examine the condition experimentally.

In 1987, a team led by Baron-Cohen found the first hard evidence that synesthetes' experiences are consistent across time. The researchers asked a synesthete to describe the color that each of 100 words triggered. A year later, they repeated the test without warning and found that the associations between words and colors that their subject described were consistent with her initial responses more than 90 percent of the time. In contrast, people without synesthesia, asked to perform the same task but with only a two-week interval between the two tests, were consistent only 20 percent of the time.

In later research, Baron-Cohen's group established that synesthesia is not only consistent across time but also concretely measurable in the brain. Using positron-emission tomography and functional magnetic resonance imaging, the researchers have found that for synesthetes who report colored hearing, visual areas of the brain show increased activation in response to sound. That isn't the case for nonsynesthetes.

Other studies have demonstrated that synesthetic perception occurs involuntarily and interferes with ordinary perception. And last summer, University of Waterloo researchers Mike Dixon, PhD, Daniel Smilek, Cera Cudahy and Philip Merikle, PhD, showed that, for one synesthete, the color experiences associated with digits could be induced even if the digits themselves were never presented. These researchers presented a synesthete with simple arithmetic problems such as "5 + 2." Their experiment showed that solving this arithmetic problem activated the concept of 7, leading their synesthete to perceive the color associated with 7.

This finding, published last July in the journal Nature (Vol. 406), was, according to Dixon, the first objective evidence that synesthetic experiences could be elicited by activating only the concepts of digits. As such, these results suggest that, at least for this synesthete, the color experiences were associated with the digit's meaning, not just its form.

Together, the evidence shows that "something is going on in the sensory areas of the brain," concludes Christopher Lovelace, PhD, a research fellow at Wake Forest University School of Medicine. "What we have to do now is try to figure out how the brain does it."
Uncertain origin
A century ago, researchers ascribed synesthesia, somewhat vaguely, to "crossed wires" in the brain. Today, despite neuroscientists' more complex understanding of brain anatomy and their sophisticated tools for tracking brain function, synesthesia's roots continue to elude understanding. Several competing theories have emerged, but all require further testing.

Baron-Cohen and his colleagues propose that synesthesia results from a genetically driven overabundance of neural connections in the brain. Ordinarily, Baron-Cohen explains, different sensory functions are assigned to separate modules in the brain, with limited communication between them. In synesthesia, Baron-Cohen and his colleagues posit, the brain's architecture is different. Synesthetes' brains, they believe, are equipped with more connections between neurons, causing the usual modularity to break down and giving rise to synesthesia.

Daphne Maurer, PhD, a psychologist at McMaster University, has further speculated that all humans may be born with the neural connections that allow synesthesia, but that most of us lose those connections as we grow.

Naropa University psychologist Peter Grossenbacher, PhD, agrees that there's likely a genetic root to synesthesia, and like Baron-Cohen's group, he and his colleagues have teamed with molecular geneticists to probe the question. But Grossenbacher and his colleagues suspect a different brain mechanism.

"We don't need to posit some abnormal architecture of connections in order to account for synesthesia," Grossenbacher argues.

Instead, he proposes that in the brains of synesthetes, "feed-backward" connections that carry information from high-level multisensory areas of the brain back to single-sense areas are not properly inhibited. Ordinarily, information processed in such multisensory areas is allowed to return only to its appropriate single-sense area. But in synesthetes' brains, Grossenbacher argues, that inhibition is disrupted somehow, allowing the different senses to become jumbled.

Grossenbacher believes his view is consistent with the fact that hallucinogenic drugs can temporarily induce synesthesia.

"I don't think that new connections are forming in the brains of those individuals for a few hours and then disappearing," he says. "What's much more sensible is that existing connections become used in a way that's neurochemically altered for a few hours."

But, Grossenbacher acknowledges, "The trouble with theorizing in this area is that we're underconstrained by data. There isn't the right kind of data, yet, to differentiate between these different theories."

Baron-Cohen agrees, "Neuroimaging is the best thing we've got at the moment, but the spatial resolution isn't good enough to allow us to see whether the individual connections in the brain are cross-wired."

Post-mortem examinations would allow closer inspection of what's different about synesthetes' brains, Grossenbacher and Baron-Cohen agree. But, so far, no known synesthetes have died and left their brains to science.
Implications
For psychologists, interest in synesthesia extends far beyond just the study of the few individuals who experience the phenomenon.

"Synesthesia taps into a lot of other domains that are more familiar to many psychologists," says Marks. "It tells us something about the nature of perception and what makes things perceptually similar to one another. Synesthesia may help us to understand how the concept of similarity is embedded within the nervous system."

In addition, Dixon suggests, the fact that synesthetic perception interferes with the perception of physical stimuli highlights an important aspect of cognition.

"We tend to think of our experiences, and especially the visual system, as being bottom-up," he remarks. "But there are many instances where meaning goes back down and influences our lower-order perception of the world. Synesthesia is just one very rare and exceptional example of that."

The possibility that synesthesia has genetic roots is equally tantalizing, says Grossenbacher--especially if it turns out that a single gene controls the condition, as some have speculated.

"If indeed something as central to mental life as [synesthesia] is controlled by a single gene, this might be rather a new kind of gene to know about," says Grossenbacher. "It would be a gene that, in either of its forms, results in a healthy human but has a profound effect on the organization of the nervous system."

At a practical level, many researchers observe, research on synesthesia will help raise the condition's visibility, reducing the risk that clinicians might mistake it as a sign of mental illness.

In addition, Grossenbacher, Lovelace and Crane--who conducts research on synesthesia while completing her doctorate in clinical psychology--are beginning to examine whether common mechanisms might underlie both synesthesia and hallucination. If so, synesthesia may be an ideal laboratory for studying those mechanisms.

"This is a group of people who would be available for research," explains Crane. "Unlike patients who experience hallucinations, synesthetes are not medicated, so you don't have that confounding factor. We're able to talk about our experiences. We offer something very valuable."

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Everyday fantasia: The world of synesthesia

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Guitar music doesn't just tickle Carol Crane's fancy--it also brushes softly against her ankles. When she hears violins, she also feels them on her face. Trumpets make themselves known on the back of her neck. In addition to feeling the sounds of musical instruments on her body, Crane sees letters and numbers in brilliant hues.

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I don't believe I have any synthete tendencies. The one that fascinates me the most is that when others can see each other, and associated a color to a person or a smell to the sight of someone.

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Before crossing the road, if I hear a car approaching, I'll stop before walking across and watch it pass. My brain associates the sounds of a car with the look of a car, so I know not to cross the street even if I haven't seen the car yet.

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I think it's interesting how two people with Synesthete tendencies can perceive the same numbers as different colors. They're seeing the same thing, but their perception is different.

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Richard Cytowic, a pioneering researcher who returned synesthesia to mainstream science, traces the historical evolution of our understanding of the phenomenon.

There is no reason to think that synesthesia hasn't existed throughout all of human history. We just don't have adequate records to make a reliable determination. Famous thinkers such as Aristotle, Johann Wolfgang von Goethe, and Sir Isaac Newton reasoned by analogy (an accepted scientific method until the end of the 17th century) across different dimensions of perception to pair, for example, a sound frequency with a given wavelength frequency of light.

The first photograph of a synesthetic individual dates from 1872. It is of eight-year-old Ellen Emerson, daughter of Ralph Waldo Emerson. The philosopher Henry David Thoreau, a close family friend, wrote to Ellen's father in 1845: "I was struck by Ellen's asking me. ... If I did not use ' colored words.' She said that she could tell the color of a great many words, and amused the children at school by doing so."

This spare description is evidence enough that Ellen Emerson was indeed a synesthete. Colored words are a common type of synesthesia. Her assumption that others also see them that way is likewise typical. Jörg Jewanski at the University of Münster notes that "since Thoreau was 'struck,' we can assume it was not just the amusing game of a child." Apparently this was the first time he had heard of such an experience, and it was "unusual to him."

Individuals typically say they have had synesthesia as far back as they can remember.

Professor Jewanski has also unearthed the first reported clinical case of synesthesia. It is in the form of an 1812 medical dissertation, written in Latin, by Georg Tobias Ludwig Sachs. As a polymodal synesthete (someone who experiences synesthesia involving more than one sense), Sachs cited examples of his "color synesthesia for letters of the alphabet, for tones of the musical scale, for numbers, and for days of the week." Sporadic medical reports followed, but these all concerned adults - a finding that raises the question, Where were all the synesthetic children in the 60 years leading up to the Emerson case? And why were they afterward in apparently short supply? After all, individuals typically say they have had synesthesia as far back as they can remember. Its consistent expression over time likewise points to roots in childhood.

Modern scientists have been studying synesthetic children in depth, including neonates, since 1980. Their investigations have influenced theories about how the phenomenon develops in the brain, and so the absence of childhood reports before the 20th century remains a historical puzzle. The term synesthesia did not exist between 1812 and 1848, but that explains only part of the gap. One consequence of the gap is that data sets from the large number of 19th-century statistical studies are completely unknown to all but a handful of researchers today. Contemporary investigators may possess superior methods, but they are liable to retread old ground if they are unaware that people working long ago had already posed, and sometimes answered, key questions about the phenomenon.

Interest in synesthesia accelerated after 1880 when the influential polymath Sir Francis Galton, Charles Darwin's cousin, wrote about "visualized numerals" in the prestigious journal Nature. Three years later he noted the strong tendency for synesthesia to run in families. Steadily, the number of peer-reviewed papers increased. In the same year that Galton's first paper appeared, the ophthalmologist F. Suarez de Mendoza published a book in French, "L'audition colorée." Not until 1927 did a German-language book on synesthesia appear, Annelies Argelander's "Das Farbenhören under der synästhetische Faktor der Wahrnehmung." A book-length treatment in English would still be decades off, but suddenly the topic seemed to fill the salons of fin de siècle Europe. Composers, painters, and poets piled on, even proponents of automatic writing, spiritualism, and theosophy. The zeitgeist of the time unfortunately emphasized the idea of sensory correspondences, which overshadowed attention to synesthesia as a perceptual phenomenon. Two famous poems of the period still taught today are "Correspondances" by Charles Baudelaire and "Voyelles" by Arthur Rimbaud. Given the cultural atmosphere during this burst of romanticism, it is easy to see how synesthesia gained an iffy reputation.

To make matters worse, behaviorism came onto the scene - an inflexible ideology that regarded the observation of behavior rather than the conscious introspection of experience as the only correct way to approach psychology. Behaviorism peaked in influence between 1920 and 1940. A marked drop in scientific papers occurred during this time, only to rebound during a second renaissance in the late 1980s.

In the 19th century and earlier, introspection was a common and respected experimental technique. But then medicine began to distinguish symptoms such as pain, dizziness, or ringing in the ears as subjective states "as told by" patients, from signs like inflammation, paralysis, or a punctured eardrum that a physician could see as observable facts. This brings us full circle back to synesthesia's fundamental lack of outward evidence that could satisfy the science of its day. Many decades after behaviorism had fallen from favor, modern science still rejected self-reports and references to mental states as unfit material for study. As a methodology, introspection was considered unreliable because it was unverifiable - again, the chasm of first-person versus third-person reports.

One reason for the persistent distrust of verbal reports is not that scientists thought people were lying about what they experienced but instead because of a remarkable discovery: All of us routinely fabricate plausible-sounding explanations that have little, if anything, to do with the actual causes of what we think, feel, and do. This must be so for reasons of energy cost, which forces the bulk of what happens in the brain to be outside consciousness.

If clinicians spoke of synesthesia at all, they spoke of vague "crossed connections" between equally ill-defined "nerve centers."

To understand this counterintuitive arrangement it helps to think of a magician's trick. The audience never perceives all the steps in its causal sequence - the special contraptions, fake compartments, hidden accomplices. It sees only the final effect. Likewise, the real sequence of far-flung brain events that cause a subjective experience or overt action is massively more than the sequence we consciously perceive. Yet we still explain ourselves with the shortcut "I wanted to do it, so I did it," when the neurological reality is "My actions are determined by forces I do not understand."

Hard as it is to imagine now, this attitude rendered all aspects of memory, inner thought, and emotion taboo for a long time. These were relegated to psychiatry and philosophy. As late as the 1970s when I trained in neurology, my interest in aphasia (a loss of language) and split-brain research got me labeled "philosophically minded" because all firsthand experience was dismissed as outside neurology's proper purview.

The science of the day was simply not up to the task before it. For any phenomenon to be called scientific it must be real and repeatable, have a plausible mechanism explainable in terms of known laws, and have far-reaching implications that sometimes cause what Thomas Kuhn called a paradigm shift. Psychology at the time wasn't up to the challenge either. It, too, was an immature science, jam-packed with ill-defined and untestable "associations." It did not yet know about priming, masking, pop-out matrices with hidden figures, or any number of optical and behavioral techniques now at our disposal that show synesthesia is perceptually real. The idiosyncratic nature of the phenomenon was a major obstacle that earlier science couldn't explain, whereas today we can account for differences among individuals in terms of neural plasticity, genetic polymorphism, and environmental factors present both in the womb and during the formative years of early childhood.

The 19th-century understanding of nervous tissue was likewise paltry compared to what we know now. If clinicians spoke of synesthesia at all, they spoke of vague "crossed connections" between equally ill-defined "nerve centers." But such tentative ideas were neither plausible nor testable. If we didn't understand how standard perception worked, then how could the science of the time possibly explain an outlier like synesthesia? It knew little about how fetal brains develop, the powerful role of synaptic pruning, or how interactions between genetics and environment uniquely sculpt each brain (which is why identical twins often have different temperaments). The enormous fields of signal transduction and volume transmission likewise remained undiscovered until the 1960s. Volume transmission is the conveyance of information via small molecular messengers and diffusible gases not only in the brain but also throughout the entire body. If you think of the physical wiring of axons and synapses as a train going down a track, then volume transmission is the train leaving the track. All these concepts were beyond our earlier comprehension.

Today we can test hypotheses about cross-connectivity and how neural networks establish themselves as needed, self-calibrate, and then disband. We do this through a variety of anatomical and physiological tools that range from tensor diffusion imaging to magnetoencephalography. As for synesthesia upending the status quo and causing a paradigm shift, it had to wait until orthodoxy could no longer object. By the early 2000s, the brain pictures that a critical establishment had demanded for decades were at last at hand, and in abundance. Critics were silenced, and long-standing dogmatic notions of how the brain is organized were out. The meaning of the paradigm shift lay in realizing just how consequential synesthesia is. Far from being a mere curiosity, it has proven to be a window onto an enormous expanse of mind and brain.

Since the early reports of Georg Sachs and Francis Galton, our understanding has changed immensely, particularly over the past two decades. There is every reason to expect that the framework for the why and how of synesthesia will continue to change. That is the nature of science: Answer one question, and 10 new ones arise. Science is never "settled," as President Barack Obama falsely liked to say. Long-entrenched ideas can be overthrown by new evidence. For example, "everyone knew" since the 1800s that stomach ulcers were caused by excess acid. Standard treatment consisted of a bland diet and surgery to cut out the stomach's eroded parts. Barry Marshall was ridiculed and dismissed by the medical establishment when he suggested in 1982 that the bacterium, Helicobacter pylori, was the true cause of ulcers. His work eventually won the 2005 Nobel Prize, and today ulcers are cured by a short course of antibiotics.

Understanding the laws behind the ability could give us an unprecedented handle on the development of language and abstract thinking.

Similarly, James Watson and Francis Crick discovered the double helix of DNA in 1953. Today, as genetics underlies all modern biology, it is astonishing that a small change in one's DNA dramatically alters one's perception of the world. The most profound question is why the genes for synesthesia remain so prevalent in the general population. Remember that about one in 30 people walk around with a mutation for an inwardly pleasant but apparently useless trait. It costs too much in wasted energy to hang on to superfluous biology, so evolution should have jettisoned synesthesia long ago. The fact that it didn't means that it must be doing something of inapparently high value. Perhaps the pressure to maintain it stays high because the increased connectivity in the brain supports metaphor: seeing the similar in the dissimilar and forging connections between the two. Understanding the laws behind the ability could give us an unprecedented handle on the development of language and abstract thinking, to say nothing of creativity.

Synesthesia has already caused a paradigm shift in two senses. For science, it has forced a fundamental rethinking about how brains are organized. It is now beyond dispute that cross talk happens in all brains; synesthetes just have more of it that takes place in existing circuits.

The other paradigm shift lies within each individual. What synesthesia shows is that not everyone sees the world as you do. Not at all. Eyewitnesses famously disagree on the same "facts." Others have different points of view than you do, and all are true. Synesthesia highlights how each brain filters the world in its own uniquely subjective way.
Richard E. Cytowic, M.D., MFA, a pioneering researcher in synesthesia, is Professor of Neurology at George Washington University. He is the author of several books, including "Synesthesia: A Union of the Senses," "The Man Who Tasted Shapes," "The Neurological Side of Neuropsychology," and "Synesthesia," from which this article is excerpted.

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Richard Cytowic, a pioneering researcher who returned synesthesia to mainstream science, traces the historical evolution of our understanding of the phenomenon.