Synesthesia
From Psy3242
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Overview
Synesthesia is a phenomenon in which one type of sensory stimuli produces hallucinations in another sensory area. It is specifically defined as being, "a sensation produced in one modality when a stimulus is applied to another modality, as when the hearing of a certain sound induces the visualization of a certain color."[1]One of the most common forms of synesthesia is seeing letters or numbers in specific colors; this type is referred to as "grapheme-to-color" synesthesia.
An example of what grapheme-to-color synesthesia might look like.
Grapheme-to-color Synesthesia
As noted, grapheme-to-color synesthesia deals with a person's visual perception of a number or letter and the subsequent involuntary perception of a color. This type of synesthetic experience tends to be relatively consistent over time (i.e. the same letters or numbers are perceived as being the same color) and because of the extent to which the visual system has been researched, it is the most commonly studied. [2]
Specific colors perceived for certain letters or numbers tend to remain consistent across different synesthetes, such as the pairing of A with red and B with blue, which may also have something to do with how common both the letters and the colors are in everyday life. Patients with synesthesia are usually unaware that others are not experiencing the same things as others and while they do see colors projected into the space in front of them, they do not confuse these colors with "real" colors that may also be present and are aware of both colors simultaneously. Most synesthetes do not see their extra perception as a problem and sometimes even describe it as helpful, especially in regards to memory and association. In fact, certain computer technologies are even utilizing "artificial synesthesia" to make their programs more accessible. [3]
Studies about Synesthesia
In an analysis of the actual perceptual existence of synesthetic colors, Palmeri et al. (2002) determined that the phenomenon is indeed real and that it sometimes interferes with performance on certain tasks. An example would be the Stroop task, in which "subjects experience significant interference when naming ink colors of written words when those words are color terms incongruent with the ink color (Palmeri, 2006). A modified Stroop test, with words printed in ink colors that were different from W.O.'s perceived synesthetic colors, was administered to the subject. W.O. experienced that same type of interference as with an average participant, indicating that there was indeed synesthetic color-binding occuring. He was also tested for increased visual search efficiency from synesthetic colors.(Palmeri, 2006).
- Visual Search Efficiency from Synesthetic Colors
The average participant would have to spend significantly longer identifying the figure within while a synesthete, with the ability to see the 2s as red, would have the image "pop out" at him.
In 2006, Peter Hancock conducted a study involving monozygotic twins and their perception of colors associated with certain numbers. While the twins didn't actually see the colors projected over the numbers, they showed remarkable similarity in the colors that they associated with given numerals. Hancock determined that their perceptions could be related both to a puzzle that they had played with when they were toddlers and to their genetic makeup as their mother also knew the "right" colors that that certain numbers should be (2006). A similar study by Witthoft and Winawer (2006) determined that people who are predisposed to synesthesia may also be "sensitive" to certain types of stimuli, such as the refrigerator magnets in this particular study, and may actual learn the grapheme-color associations that they will later have and that this "early-processing" finding can possibly be generalized across the synesthetic population.
Disinhibited Feedback Model of Synesthesia
This model of synesthesia relates to the idea that sensory input travels along pathways in the brain and creates perceptions but that the impulses can also travel in the opposite direction and established ideas or pathways can influence earlier sensory systems. It is possible that this is also how "learned" synesthesia can exist. [4]
References
Hancock, P. (2006). Monozygotic twins' colour-number association: A case study. Cortex, 42, 147-150.
Palmeri, T. J. et al. (2002). The perceptual reality of synesthetic colors. PNAS, 99(6), 4127-4131.
Witthoft, N. & Winawer, J. (2006). Synesthetic colors determined by having colored refrigerator magnets in childhood. Cortex, 42, 175-183.
External Links
http://youtube.com/watch?v=KApieSGlyBk&feature=related
Videos
http://www.youtube.com/watch?v=veoN1mh7RME
Just an interesting tidbit I learned in my Autism and Behavior Analysis class. Some people with Asperger's Syndrome tend to display Synesthisia as a symptom of the mental disability. I found that interesting and thought of this class. ~Hannah
