Synesthesia -- What Is It?

An interest in colored hearing dates back to Greek antiquity, when philosophers asked if the color (chroia, what we now call timbre) of music was a quantifiable quality. (J. Gage, Colour and Culture. Practice and Meaning from Antiquity to Abstraction,1993). Isaac Newton proposed that musical tones and color tones shared common frequencies, as did Goethe in his book, Theory of Color. So what about the blending of the human senses? Is this nothing other than association and conditioning that causes some things like color and sound to share common ground? Or is it, sometimes, something much, much more?

According to Ker Than, LiveScience staff writer, "For most of us, the boundaries between our bodily senses are clear-cut and rigid. But for a few rare individuals, the demarcation between vision and hearing, or between taste and touch, are less solid, with one bleeding into the other." These people have a condition called "synesthesia."


Synesthesia is a neurologically based phenomenon in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway.(Richard E.Cytowic, Synesthesia: A Union of the Senses, 2002) People with his condition, in which two or more senses are crossed, can experience unique blends of sensory perception. Some see colors when listening to music, while others associate tastes with shapes or words with colors. People with the phenomenon of synesthesia could help scientists unravel how perception works in the rest of us.

What Causes Synesthesia?

The exact cause of synesthesia is still unknown, but a popular hypothesis by Daphne Maurer and Catherine Mondloch at McMaster University in Ontario, Canada, suggests that all of us begin life as synesthetes. The researchers believe our infant brains once contained connections between different sensory areas, and that these connections became pruned or blocked as we matured. "For synesthetes, this process doesn't take place fully, and some of those connections are left active," Julia Simner added. (Perception, August 2006)

True neurological synesthesia is involuntary and automatic. Synesthesia runs strongly in families, but the precise mode of inheritance has yet to be ascertained. Synesthesia is also sometimes reported by individuals under the influence of psychedelic drugs, after a stroke, during a temporal lobe epilepsy seizure, or as a result of blindness or deafness.

Estimates of the number of individuals with synesthesia vary: one of commonly cited study reports the condition at about 1-in-2,000, with a heavy skew toward females, but in the recent study (Perception, August 2006), Simner and colleagues found that "1 out of 23 people in the UK—or about 4 percent of the population—have at least one form of synesthesia." (Ker Than, LiveScience, November 22 2006)

How Many Forms of Synesthesia Exist?

Synesthesia can occur between nearly any two senses or perceptual modes.Over 60 types of synesthesia have been reported by people,but only a fraction have been evaluated by scientific research. (Cretien van Campen, The Hidden Sense: Synesthesia in Art and Science, 2007)

Even within one type, synesthetic perceptions vary in intensity and people vary in awareness of their synesthetic perceptions. So, defining synesthesia in an individual is difficult, and the majority of synesthetes are completely unaware that their experiences have a name. (Noam Sagiv and Lynn Robertson, Synesthesia: Perspectives from Cognitive Neuroscience, 2005)

For example, synesthetes who see colors when hearing sounds tend to see light colors for high-pitched sounds and dark colors for low-pitched ones. "This is exactly the same type of association that we all make if we're forced to make a judgment," recent synesthesia study team member Julia Simner of the University of Edinburgh in the UK told LiveScience. "If I play the top note of a piano, and ask if that's a light yellow or a deep, dark purple, you're probably going to say it's a light yellow sound." 

Many people with synesthesia use their experiences to aid in their creative process, and many non-synesthetes have attempted to create works of art that may capture what it is like to experience synesthesia.

Here are some forms of synesthesia:

1. Grapheme - Color Synesthesia or Color-graphemic Synesthesia in which letters or numbers are perceived as inherently colored. (Rich AN, Mattingley JB ,January 2002).

^{2. Ordinal Linguistic Personification in which numbers, days of the week and months of the year evoke personalities. (Simner J. Holenstein, April 2007)}

3. Spatial - Sequence, or Number Form Synesthesia in which numbers, months of the year, and/or days of the week elicit precise locations in space (for example, 1980 may be "farther away" than 1990 or may have a three-dimensional view of a year as a map (clockwise or counterclockwise). (Seron X, Pesenti M, Noël MP, Deloche G, Cornet JA, "Images of numbers, or "When 98 is Upper Left and 6 Sky Blue," Cognition 44, August 1992)


4. Visual Motion - Sound Synesthesia which involves hearing sounds in response to visual motion and flicker.(Saenz M, Koch C., "The Sound of Change: Visually-induced Auditory Synesthesia, Current Biology, August 2008)

A Very Unique Synesthesia


Some people actually do have words "on the tip of their tongue." An extremely small number of so-called "synesthetes" can actually "taste" words. Lexical - Gustatory synesthetes can taste a word before they ever speak it as the word's meaning, not its sound or spelling triggers this taste sensation. (Nature, November 23 2006) The individual words and the phonemes of spoken language evoke these taste sensations in the mouth. These sensations most likely originated during vocabulary acquisition, since they are guided by learned linguistic and conceptual knowledge

The research suggests that these synesthetes develop their word-taste associations at a young age and are constrained by early food experiences. Yet, the associations persist into adulthood. Also, since a word’s sound determines its taste, synesthetes speaking non-English languages likely have completely different word-taste associations.

Simner said that most non-synesthetes, if asked to remember a list of word-taste associations, might accurately recall about a quarter of them two weeks later. "Synesthetes are accurate 100 percent over many, many, many years—over decades even," she said.

Here is a quote from Amelia Fedo, administrator of the Facebook group "Lexical - Gustatory Synesthesia."

 

Lexical-Gustatory Synesthesia

"I don't taste every single word in the English language. Roughly 80% of words have tastes for me. Some tastes are more intense, easy-to-name, or clear-cut than others. The tastes are not always necessarily food; sometimes they are metallic, plasticky, papery, woody, gritty, etc. Texture, consistency, etc. is often important, but only in the mouth--what is known in the food industry as "mouthfeel." (A kind of silly, almost Newspeakish neologism, but whatever.) Often groups of words united by similar sounds--especially ones with cognate tastes--will share similar tastes, usually varying subtly. Fairly often, too, I will not taste the whole word or even morpheme as a unit, but individual phonemes or syllables. This will result in a medley of tastes for a single word, but the tastes never actually mix together, they simply combine as individual, differentiated units to form a larger piece, like building blocks. Note that they do not combine physically because no chemoreceptors are physically being activated, it is simply in my brain, so it's different kind of gustation than actual eating and new and weird results are possible."