Sound symbolism in synesthesia: evidence from a lexical-gustatory synesthete.

Synesthesia is a condition in which perceptual or cognitive stimuli (e.g., a written letter) trigger atypical additional percepts (e.g., the color yellow). Although these cross-modal pairings appear idiosyncratic in that they superficially differ from synesthete to synesthete, underlying patterns do exist and these can, in some circumstances, reflect the cross-modal intuitions of nonsynesthetes (e.g., higher pitch sounds tend to be "seen" in lighter colors by synesthetes and are also paired to lighter colors by nonsynesthetes in cross-modal matching tasks). We recently showed that grapheme-color synesthetes are more sensitive to sound symbolism (i.e., cross-modal sound-meaning correspondences) in natural language compared to nonsynesthetes. Accordingly, we hypothesize that sound symbolism may be a guiding force in synesthesia to dictate what types of synesthetic experiences are triggered by words. We tested this hypothesis by examining the cross-modal mappings of lexical-gustatory synesthete, JIW, for whom words trigger flavor experiences. We show that certain phonological features (e.g., front vowels) systematically trigger particular categories of taste (e.g., bitter) in his synesthesia. Some of these associations agree with sound symbolic patterns in natural language. This supports the view that synesthesia may be an exaggeration of cross-modal associations found in the general population and that sound symbolic properties of language may arise from similar mechanisms as those found in synesthesia.