"Hearing Colors, Tasting Shapes" by Vilayanur S. Ramachandran & Edward M. Hubbard. www.sciam.com 4/25/2003
For people with synesthesia, the five senses (touch, hearing, taste, vision, and smell) get mixed up instead of remaining separate. These otherwise normal people might see printed black numbers in color, or smell flowers when listening to music. The first scientific description was published by Francis Galton, in an 1880 issue of the journal Nature. But the phenomenon has often been dismissed as a trick of memory, a symptom of hallucinogen use, or outright fakery.
The authors of the current review designed puzzle-like experiments that subjects could only solve if they, in fact, perceived the world as they claimed. For example, in a field of black number 5's, black number 2's were arranged in a triangle shape. Normal people had trouble picking out the triangle. To synesthetes, the 2's actually appeared to be a different color from the 5's, and so the triangle was easily distinguished from its background.
The cause appears to be some form of "cross-wiring" or chemical transmitter "cross-activation" of higher order sensory processing in the brain. The authors cite previous research as showing synesthesia to be seven times more common in "creative" people than in the general population, and suggest a link between synesthesic thinking and aptitude for metaphor. They note that all humans have this ability to some degree, and speculate that there may be an evolutionary link between cross-modal (across senses) synthesis of experience, high-level perceptual thinking, and the human facility with language and abstraction.
For people with synesthesia, the five senses (touch, hearing, taste, vision, and smell) get mixed up instead of remaining separate. These otherwise normal people might see printed black numbers in color, or smell flowers when listening to music. The first scientific description was published by Francis Galton, in an 1880 issue of the journal Nature. But the phenomenon has often been dismissed as a trick of memory, a symptom of hallucinogen use, or outright fakery.
The authors of the current review designed puzzle-like experiments that subjects could only solve if they, in fact, perceived the world as they claimed. For example, in a field of black number 5's, black number 2's were arranged in a triangle shape. Normal people had trouble picking out the triangle. To synesthetes, the 2's actually appeared to be a different color from the 5's, and so the triangle was easily distinguished from its background.
The cause appears to be some form of "cross-wiring" or chemical transmitter "cross-activation" of higher order sensory processing in the brain. The authors cite previous research as showing synesthesia to be seven times more common in "creative" people than in the general population, and suggest a link between synesthesic thinking and aptitude for metaphor. They note that all humans have this ability to some degree, and speculate that there may be an evolutionary link between cross-modal (across senses) synthesis of experience, high-level perceptual thinking, and the human facility with language and abstraction.

