Lexical-gustatory synesthesia

Lexical-gustatory synesthesia is one of the rarer forms of synesthesia, in which spoken or written words evoke vivid sensations of taste, sometimes including temperature and texture (e.g., for lexical-gustatory synesthete JIW, 'jail' tastes of cold, hard bacon). This form of synesthesia was first documented in 1907 in both Italy and the United States, but has only recently become the topic of scientific investigation.

Experiences
James Wannerton, a lexical-gustatory synesthete reports, "Whenever I hear, read, or articulate (inner speech) words or word sounds, I experience an immediate and involuntary taste sensation on my tongue. These very specific taste associations never change and have remained the same for as long as I can remember".

Experimental studies
Jamie Ward and Julia Simner have extensively studied this form of synesthesia, and have found that the synesthetic associations are constrained by early food experiences. For example, synesthete JIW has no synesthetic tastes of coffee or curry, even though he eats them regularly as an adult. Conversely, he often tastes certain breakfast cereals and candies that he ate as a child, but which are no longer sold.

Synesthetic tastes tend to be triggered by the corresponding food-name (e.g., for synesthete JIW, the word 'mince' triggers the taste of mince) as well as by words that share phonemes (i.e., speech sounds) with that food-name (e.g., 'prince', 'cinema'). Careful analyses show that each taste can be traced to a set of critical phonemes (e.g., /I/ & /n/ & /s/ for JIW's taste of mince). Other tastes, though, have less obvious roots (e.g., /f/ triggers sherbet for JIW). To demonstrate that tastes tend to be unrelated to spellings, Ward and Simner showed that, for JIW, the taste of egg is associated to the phoneme /k/, whether spelled with a c (e.g., accept), k (e.g., York), ck (e.g., chuck) or x (e.g., fax). Another source of tastes comes from semantic influences, so for example, the word "blue" might taste "inky". Recent work shows that merely thinking about the trigger word can cause the synesthetic taste sensation. Simner and Ward (2006) showed that tastes are experienced when synaesthetes are in a tip-of-tongue for the triggering word.

Neural basis
Lexical-gustatory synesthesia may be due to increased connectivity between adject regions of the insula in the depths of the lateral sulcus involved in taste processing that lie adjacent to temporal lobe regions involved in auditory processing.

In Art
The novel "Bitter in the Mouth" by Monique Truong (Chatto & Windus/Random House, 2010) deals with the experience of lexical-gustatory synesthesia by the main character.