No. 68: Mar-Apr 1990
In the January 4, 1990, issue of Nature, G. Humphreys reviews a book that is just too expensive for us to consider buying. The title is: Synesthesia; A Union of the Senses. It costs $75 and is published by Springer/Verlag. The review, however, is expansive and provides some facts about synesthesia worth passing on to our readers.
Syesthesia is an "oddity" of human perception in which words, musical instruments, objects, concepts, evoke sensations sharply different from what is actually being processed by the brain. For example, specific musical tones elicit specific color sensations; that is, B-flat evokes the color green; A-sharp, yellow, etc. Or the phenomenon may be more complex, with Mozart being green; Wagner, red, etc. Most "synesthetites" seem to experience colors, but geometrical figures sometimes appear in response to particular stimuli. As for the stimuli that call forth these exotic sensations; they are usually music or numbers. To some synesthetites, the cardinal numbers are associated with specific colors.
The books's author is R.E. Cytowic, and he has provided some very interesting observations about synesthetites: There is much consistency among them; that is, if the number 5 evokes a red sensation with one, it does with most others, too. Also, synesthetites seem to run in families. Perhaps most significant is the observation that synesthetic experiences seem to be correlated with changes in cortical blood flow!
(Humphreys, Glyn; "Higher Sight," Nature, 343:30, 1990.)