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Taste the Rainbow: Synaesthesia

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Biology 202
2006 First Web Paper
On Serendip

Taste the Rainbow: Synaesthesia

Brom Snyder

They walk among us, perhaps you work with one, maybe you listen to the music they create, quite possibly you read the poetry they write, or you have heard them comment that someone's name is "green" when you know for a fact they are talking about Mr. James down the road; who are these mysterious humans, are they talking in code? Are they members of an organization bent on overthrowing the government? Fear not America, they are merely synaesthetes. A synaesthete is someone who experiences synaesthesia, a condition where one stimulus causes two senses to respond to it, its literal translation is "union of senses", and is also sometimes described as the "neurological mixing of the senses." (1)(2) The most common types of synaesthesia involve numbers or letters being a certain color whenever observed by the synaesthete(called grapheme synaesthesia) or an auditory stimulus triggering the perception of a certain color by the synaesthete. (2)(3) These are not the only types of the synaesthesia: tactile sensations or colors triggering tastes, and certain smells eliciting other sensations are other examples of synaesthesia. This phenomena is can be induced by using drugs like LSD or mescaline, but also occurs naturally in the human population with a frequency scientists estimate of around 1 in 2000, or .05 percent. Some estimates place the frequency as high as 1 in 200. (2) (3) In fact many of famous artists of the past 100 years were synaesthetes, including Jimi Hendrix and Vladimir Nabokov. (1)

So what is going on the brain of someone with synaesthesia? For people who experience grapheme synaesthesia is there cross wiring between the parts of the brain that process color and numbers? Many researchers think this a reasonable explanation because both color and numbers are first processed in the fusiform gyrus and then near the angular gyrus; therefore a crossing of neural pathways could induce both parts of the brain to process the signal, causing numbers to be a certain colors. Vilayanur Ramchandran and Edward M. Hubbard, neuroscientists and synaesthesia researchers, advocate another possibility; an imbalance of chemicals between the areas of the brain that process numbers and colors. The various regions of the brain excrete chemicals which inhibit other parts of the brain from processing signals. If not enough of the inhibitor chemical is produced by one region of the brain there is the possibility that another region of the brain will also start processing the signal, resulting in two parts of the brain that normally do not process the same signals both processing the signal. For those experiencing grapheme synaesthesia it could be due to a chemical imbalance between the parts of the fusiform gyrus and the angular gyrus promoting excess communication between the regions of the brain. This interaction would result in response whereby the number would be a certain color. (4)

Numerical sequences appear to play an integral role in grapheme synaesthesia. Hubbard and Ramchandran conjecture " the abstract concept of numerical sequence that drives the color, rather than the visual appearance of the number." (4) This hypothesis accounts for reports the some synaesthetes associate colors with days of the week and months. (4) Although they Hubbard and Ramchandran do not discuss it, this hypothesis also makes sense in the context of the synaesthetes associating color with letters and musical keys. Although they are not based on numbers, both letters and musical keys are well-defined sequences, thus explaining why some synaesthetes associate them with colors. One problem with Hubbard and Ramchandran's sequence hypothesis is none of the synaesthetes studied associated colors with Roman numerals. (4) If numerical sequences were a primary factor behind the expression of synaesthesia it seems strange that Roman numerals would not cause grapheme synaesthesia in at least some synaesthetes. One possible explanation for the lack of grapheme synaesthesia concerning Roman numerals could be that children do not learn to count in Roman numerals or use them in mathematical contexts often when their brains are developing. Arabic numerals, days of the week, the order of the months, and the alphabet are all sequences that children learn at a relatively young age and are constantly exposed to. In contrast, Roman numerals might be learned one day in math class and then promptly not used with the possible exception trying to determine whether it was Super Bowl 33 or 37 that year. It would be interesting to examine whether a child taught to count and do math with Roman numerals would develop grapheme synaesthesia associated with Roman numerals, it seems likely.

Synaesthesia offers possible enlightenment to those who attempting to understand the origin of creativity and the development of language. Synaesthesia proves that the brain is capable of making arbitrary connections between completely unrelated things, like the number 5 and the color red. This process is similar to the creation of metaphors, where two seemingly unrelated things are linked together (i.e. "your eyes are like a foggy morning"). If people experiencing synaesthesia are experiencing an excess of communication between parts of the brain caused by a chemical imbalance, creativity can be explained as excess communication between various parts of the brain leading to the linkage of apparently unrelated things, sounds, colors, textures, leading to the emergence of relationships previously nonexistent. (4) The random connections observed in synaesthesia also could contribute to a greater understanding of the development of language. Language takes concrete things, things observed by the five senses, and then arbitrarily assigns them a sign, the sign is nothing but a placeholder. When viewed like this, it appears as if language could have initially been a form of synaesthesia whose connections could be taught, thus the emergence of language as a form of communication.

Synaesthesia provides a fascinating look into how the brain works. The seemingly random nature of the connections within different areas of the brain as evidenced by synaesthesia offers an explanation for how creativity and language work and developed. On the other hand, synaesthesia may not provide the answers to reasons for the emergence of creativity and language within man, the seemingly random connections made in the brains of synaesthetes may contain an undiscovered pattern.



1)Synaesthesia, an online encyclopedia
2)"Synaesthesia –union of the senses" by Adrianhon Feb 21st 2003,
3) Harrison, John Synaesthesia: The Strangest Thing (Oxford, Oxford University Press, 2001)
4) Vilayanur Ramchandran and Edward M. Hubbard "Hearing Colors and Tasting Shapes" April 15th 2003,


Comments made prior to 2007

I was thinking recently about a strange problem I had as a child, and how it affected my ability to learn to read and stay focused at school. My junior years in school were in the 70s for the most part and my guess would be that no one would have understood this problem back then - nor would i have ever brought it up, simply because when you are a child who is born with some kind of glitch in your brain, you don't know that it is different for anyone else.

I found it very difficult to learn to read as each letter of teh alphabet for me would produce a color in my mind, and when letters were placed together to form words, the words had colors of their own. The most pronounced of these for me were the days of the week. At almost 40, I still see the same colors for each day of teh week that I did as a child. It's more than a sight in the monds eye however, it is a feeling. I can feel the colors. I now have an eight year old son with OCD qualities, who mentioned colors for the days of the week to me the other day. I hadn\'t thought about it much for some time, but he recited the days of the week and their associated colors for me, and they are the same colors as mine. Not one miss!

How is this possible? ... JS, 27 February 2007