Mixed Signals

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Biology 202

2006 Second Web Paper

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Mixed Signals

Amber Hopkins

Throughout history, poets, composers, and artists of all types have used metaphors to create cross-sensory experiences in their works. However- instead of trying to merely create this experience in themselves and in others, many of these artists were trying to explain to the world the experiences they had in response to certain stimuli. This phenomenon, known as synaesthesia, stemming from the Greek, syn = together + aisthesis = perception,) is the "involuntary physical experience of a cross-modal association. That is, the stimulation of one sensory modality reliably causes a perception in one or more different senses" (1) .

Synaesthesia occurs predominantly in females, people who are left-handed, and within families. The pattern in which synaesthesia occurs is consistent with x-linked or autosomal dominant transmission, so either parent is capable of passing this trait to their offspring (1) .. The criteria for it to be seen as full synaesthesia are as follows: one stimulus always evokes a certain perception, the perception occurs involuntarily, the perceptions are individual: every synaesthete has their "own" colors and shapes, the perceptions are irreversible: a 7 might evoke the color blue, but the color blue doesn't evoke a 7, the perceptions are permanent: they begin at child age and don't change throughout life (2) ..

There are various forms of synaesthesia, different pairings of the senses involved in each particular case. The most common form is Grapheme-color synaesthesia, seeing colors in response to hearing or reading a letter or number. Other forms can include seeing colors in response to sounds, smells, tastes, or pain, tasting sounds or smells, smelling sights, etc (3) .. In Grapheme-color synaesthesia, there is no correlation between the colors experienced and the letters seen between different synaethetes (people exhibiting synaesthesia). Rather, each tends to associate different colors with each letter. However, surveys done do show that some letters have a tendency towards one color over the others- O is very often perceived as white, and A is often perceived as red. However, these trends are much more prevalent in vowels than in consonants (4) .. An interesting suggestion was posed, however, in one synaethetes memory of an experience she shared with her father, also a synaethete. She said that "sitting at dinner with my family one evening, I commented that "The color five is yellow." There was a pause, and my father said, "No, it's yellow-ochre." And my mother and my brother looked at us like, 'this is a new game, would you share the rules with us?' And I was dumbfounded. So I thought, "Well." At that time in my life I was having trouble deciding whether the number two was green and the number six blue, or just the other way around. And I said to my father, "Is the number two green?" and he said, "Yes, definitely. It's green." And then he took a long look at my mother and my brother and became very quiet. Thirty years after that, he came to my loft in Manhattan and he said, "you know, the number four *is* red, and the number zero is white. And," he said, "the number nine is green." I said, "Well, I agree with you about the four and the zero, but nine is definitely not green!"" (5) .. This implies that perhaps to some extent, the colors a synaethetes experiences in regards to certain stimuli might also be determined genetically.

Another question posed by the observation that synaesthesia is genetically determined lies in its evolution. First, when a synaethete is observed experiencing synaesthesia, we would typically expect some cortical area(s) to "light up." Richard Cytowic, observed however, that "cortical metabolism actually plummets during synaesthesia. Such a decrease is impossible to obtain in a normal person with, for example, a drug. Even during an activation trial with amyl nitrate, which subjectively intensifies the synaesthetic experience, he observed that the patient's regional blood flows are decreased compared to baseline. Normally, any physical or mental task, or any activation procedure (e.g., drug administration, carbon dioxide or oxygen inhalation), increases blood flow by five to ten percent." This led Cytowic to the conclusion that because the patient's thinking and neurological exam were unimpaired, the area of the brain most involved in synaesthetic experiences was not the cortex, but rather the limbic system, which is more primarily involved in emotion, memory, and attention. (1) Interesting to note, however, is that only in mammals is the limbic system seen in its most developed form. Thus, are animals below the level of mammals incapable of the synaesthetic experience?

Further exploration into the evolution of synaesthesia poses the question as to the necessity of its evolution. The symptoms of synaesthesia do not appear to hinder the development or existence of those experiencing them- rather the opposite in many cases! One synaesthete said for example "What synaesthesia is about for me is an extra way of perceiving the world. Because of that additional dimension, the parts of the world that I perceive in this special way are parts I hold most dear...Equally important, however, is the idea that the creative person is able to use her unique abilities, ridiculed though they may be, to make not only a living but also a significant contribution to the world" (6) .. Why, then, is synaesthesia not more common? To answer this question, we must look at a more extreme case, where the synaesthete "not only sees colours when she hears sounds, but suffers from the reverse: she hears sounds whenever she sees colours. Here, the word "suffers" is used advisedly, as this form of synaesthesia leads to massive interference, stress, dizziness, a feeling of information overload, and a need to avoid those situations that are either too noisy or too colourful...Here then, we have a clear case of synaesthesia leading to social withdrawal, and interference with ordinary life" (7) ..

The most recent views of synaesthesia are proposing that in reality, everyone is a synaesthete. Looking at the development of the brain, evidence is suggesting that "babies experience sensory input in an undifferentiated way. Sounds trigger both auditory and visual and tactile experiences. A truly psychedelic state, and all natural - no illegal substances play a role. ...suggests that this results in a sensory confusion for the infant... The notion would be that following an early initial phase of normal synaesthesia, the different sensory modalities become increasing modular (Fodor, 1983), presumably because modularity leads to more rapid and efficient information processing, and is therefore highly adaptive" (7). Thus, adult synaesthetes might therefore have not gone through the process of modularization, causing them to continue to experience sensory input in an undifferentiated way. Cytowic puts it into this perspective- "Do the elemental qualities of synaesthesia, as partially represented by the form constants, represent "building blocks" or "modules" of cognitive science in which a perception is assembled like modeling a statue from bits of clay? Or is perception holistic, constrained by sensation as it unfolds from within? If so, then perception is like sculpting from a block of marble, exposing the statue within it by removing extraneous bits. In this view, synaesthesia is the conscious awareness of a normally holistic process of perception that is prematurely displayed. That is, it is awareness before the terminal target, before the final stage of neural transformation and mental mediation. If this is correct, then we are all unknowingly synesthetic" (1).

1) Synesthesia: Phenomenology And Neuropsychology , A review of current knowledge
2) Wikipedia , article on Synaesthesia
3) Types of Synesthesia , Analysis of 778 case reports
4) Trends in Colored Letter Synesthsia , Analysis of color frequencies
5) Synesthetes Perspectives , Carol's thoughts on her synaesthesia
6) Colored Letters , Demonstration of aspects of synaesthesia
7) Is There a Normal Phase of Synaesthesia in Development?, Analysis of synaesthesia from infancy into adulthood

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