Four percent of the population, when seeing number five, also see color red. Or hear a C-sharp when seeing blue. Or even associate orange with Tuesdays. And among artists, the number goes to 20-25 percent! This neurologically-based condition is called synesthesia, in which people involuntarily link one sensory percept to another. The colors, sounds, numbers, etc. differ among people (for example, you might see five in red, while someone else sees it in orange), but the association never varies within a person (that is, if five for you is red, it will always be red). There is a surprising overall agreement among synesthetes, however.
The primary perspective of the cause of synesthesia is a mutation that causes defective pruning between areas of the brain that are ordinarily connected only sparsely. Therefore areas that are disconnected within a human brain retain certain connections in synesthetes, which causes unusual associations. The location of gene expression leads to two different types of synesthetes: If the gene is expressed in the fusiform gyrus, the brain area concerned with perception, a perceptual synesthesia results, in which people will actually perceive, for instance, a number five colored in red. If, however, the gene is expressed in the angular gyrus, the brain area involved in processing concepts, a conceptual synesthesia results, in which people will not physically see the color red when presented with a number five, but will nevertheless experience an association between the two concepts.
I must admit, I am a conceptual synesthete (but only for certain numbers). Two is a nice light cream color; three is bright green; four is beige with a bit of light brown; five is definitely blood red; seven is ice blue. Eight wants to be something, but it’s difficult… Nine is dark, almost black. I don’t physically see colors, but when numbers are colored in something other than my associations, it causes some distress. I also paint and am very sensitive to colors and sounds in general.
I also believe that even though perceptual synesthesia may be relatively rare, it does not mean that a subtler cross-sensory undercurrent is nonexistent. I would not be surprised if many creative individuals were conceptual synesthetes. They may not necessarily physically perceive the connections between the percepts, but nevertheless may exhibit the facility in linking seemingly unrelated realms in order to highlight a hidden deep similarity. For example, in a sample of normal university students, those who had higher scores on the remote associates task (which requires finding a common word that can be combined with each of the three problem words to form a common compound or a phrase: e.g., ‘shine, beam, struck;’ solution — ‘moon’) showed stronger associations between colors and pure tones than people with lower scores on the same test. Similarly, synesthetes outperformed controls on the remote associates test. In addition, examination of poetry of Poe, Swinburne, Shelley, Blake, and Keats revealed that they all employed synesthetic usage in their poetry. These findings indicate that cross-sensory linkages may be associated with creative thinking.
I would be glad to hear from synesthetes, as well as from individuals involved in creative pursuits. What are your experiences? How do you perceive the world? How do your experiences affect your daily life?
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Ramacharndran, V. S., Hubbard, E. M., & Butcher, P. A. (2004). Synesthesia, cross-activation and the foundations of neuroepistemology. In G. Calvert, C. Spence, & B. E. Stein (Eds.), The handbook of multisensory processes (pp. 867-883). Cambridge, MA: MIT Press.
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Ward, J., Thompson-Lake, D., Ely, R., & Kaminski, F. (2008). Synaesthesia, creativity and art: What is the link? British Journal of Psychology, 99, 127-141.