I got a lot of comments on my previous post on synthesia, so it seems there’s some interest there. Check out this post on Cognitive Daily about a study of the rarest form of synthesia – tasting words.
For more common (or rather, less uncommon) forms of synesthesia, the most convincing evidence that it’s real comes from studies showing that synesthetic associations are stable. If “A” is associated with the color blue now, it will still be associated with blue six months from now. What’s more, sometimes the letter-color associations are the same for different people. With only one example to study, this type of evidence is harder to come by, but at least Gendel could test TD at different times and see if her associations were stable.
Gendel presented TD with 806 randomly selected words, and 222 nonsense words created from English-language sounds. She was asked to write down what taste (if any) she associated with each word, and rate the strength of the association. Then the test was repeated three months later. Almost 50 percent of the time, TD experienced a taste sensation accompanying the word. In those cases, 88 percent of the time that sensation was identical or nearly identical three months later. Stronger taste sensations were significantly more likely to be repeated at the end of the study.