Christopher Shea, writing in the Wall Street Journal, recently reported on an experiment that asked whether it was possible to teach oneself to be synesthetic. The question is important—and the answer would be fun if it were true.
Currently 1 in 23 individuals possess the synesthesia gene, and 1 in 90 express the common grapheme synesthesia in which letters and numerals printed in black are nonetheless perceived in color. Other common types are seeing sounds, tasting words, and seeing things that run in sequences—the alphabet, history dates, shoe sizes, temperature—as having a place in three-dimensional space. Who might not wish to experience one of these offbeat and unusual ways of perceiving the world?
And that’s what a research team in Amsterdam set out to ask—is it possible for individuals not born with the trait to learn it? Given that the synesthesia gene alters the perception of one’s physical world, they attempted to induce “synesthesia in reverse” by changing the physical world.
They gave 15 non–synesthetes specially prepared books to read in which the letters “a,” “e,” “s,” and “t” were printed in red, orange, green, and blue inks. (Participants had expressed a preference for these colors.) A Stroop effect appeared after viewing 49,000 words, indicating, the authors claim, that it is possible to learn “letter-color associations through reading in color.” They further claim this as the “the first evidence” of this being so.
To my mind asking whether one can “learn” synesthesia is mistaken, and this study doesn’t make sense nor do I think it necessarily proves anything. For one thing, whatever perceptual experience may accompany the learning of letter–color pairs, it would seem to be totally unlike that which characterizes naturally–occurring synesthesia. That is, the “qualia” of the two states are worlds apart.
Secondly, why one would want to go to the trouble of doing this? That is, what is the payoff? As far as I can see from reading the details of “Pseudo–synesthesia through reading books with colored letters” in PLoS One 7(6):e39799, tests subjects don’t benefit in any discernible way. They acquire neither the elevated memory typical of most synesthetes, nor any of the secondary personality characteristics typically seen.
As for the claim of providing the first evidence that letter-color pairs can be deliberately learned, the late Jeffrey Gray demonstrated this in 2002 during his studies of synesthetic qualia, “qualia” being one’s subjective experience of what it is to perceive the quality of red, sweet, vanilla, round, sharp, and so forth. His paper “Implications of synaesthesia for functionalism” appeared in the Journal of Consciousness Studies 9(12):5–31.
As I see it, the meager results of the Danish study don’t warrant claims that synesthesia can be purposely learned. A tiny fraction of grapheme synesthetes appear to have been imprinted at an early age, but that is a different story.