Even unspoken words can have a ‘taste’

By Ker Than

updated 9:36 p.m. ET Nov. 22, 2006

For most of us, the boundaries between our bodily senses are clear-cut and rigid. But for a few rare individuals, the demarcation between vision and hearing, or between taste and touch, are less solid, with one bleeding into the other.

These people have a condition called "synesthesia," in which two or more of the senses are crossed. Some see colors when listening to music, while others associate tastes with shapes or words with colors. A very small number of synesthetes can "taste" words.

A new study finds that individuals with this last form of synesthesia — called "lexical-gustatory" synesthesia — can taste a word before they ever speak it, and that the word's meaning, not its sound or spelling, is what triggers this taste sensation. The finding, detailed in Thursday's issue of the journal Nature, could help scientists unravel how perception works in the rest of us.

Chocolate phonographs
In the experiment, the researchers showed six lexical-gustatory synesthetes images of objects they were familiar with, but which they didn't normally encounter. The images included a platypus, a gazebo, an artichoke, a metronome and a sextant. Doing this induced a "tip-of-tongue" state in the participants, during which they recognized the object but couldn't immediately identify it.

"At the moment they're trying to find the word, we ask them two things: whether they knew any part of the word at all, and what it tasted of," said study team member Julia Simner of the University of Edinburgh. "I remember one participant, we showed her a phonograph, and she said 'I know what that is … um … um … Oh! I'm tasting Dutch chocolate and I don't know why!'"

To ensure that the synesthetes' word-taste associations weren't arbitrarily chosen, Simner and her colleague Jamie Ward asked them to repeat the associations after the trial.

They also cold-called participants, up to two years later, and asked them the same questions. "We phone the synesthetes completely out of the blue," Simner said. "We say ''Hello, we did this study on you. … Can you tell me what 'phonograph' tastes of?' and they say, 'Yeah, it tastes of Dutch chocolate."

Simner said that most non-synesthetes, if asked to remember a list of word-taste associations, might accurately recall about a quarter of them two weeks later.

"Synesthetes are accurate 100 percent over many, many, many years — over decades even," she said.

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