Grapheme-color (GC) synesthesia refers to the consistent and involuntary association of phonemic orthography with color; for example, the letter ‘A’ can be perceived as red regardless of the text’s color. Although little is known about how GC synesthesia influences speech perception, one large-scale study (Cuskley et al. (2019). “Cross-modal associations and synesthesia: Categorical perception and structure in vowel-color mappings in a large online sample.” Behavior Research Methods, 51(4), 1651–1675) has shown that such synesthetes also associate vowel sounds with different colors in their language. If this response is triggered by sound, synesthetes may have an advantage over non-synesthetes in discriminating non-native vowel contrasts through an additional perceptual cue to the contrast. We tested this hypothesis in English speakers using an ABX task. A total of 28 participants (9 synesthetes) learned 3 French vowel contrasts, including 2 that do not exist in English. In Exp. 1, the task was purely auditory. In Exp. 2, auditory stimuli were associated with a grapheme. The findings were that non-synesthetes performed better than synesthetes in Exp. 1, but no group differences appeared in Exp. 2. Preliminary study results undermine our hypothesis and suggest that color-sound associations in synesthesia may be secondary to color-grapheme associations.
Lindon et al. (Wed,) studied this question.