“I have to translate the colors”: Description and implications of a genuine case of phoneme color synaesthesia

•In linguisitc synesthesias, the oral dimension is under explored.•The genuineness of a phoneme color synesthesia is evaluated with different linguistic units.•This form of synesthesia is linked to an atypical speech processing.•This form of synesthesia is described in a person who also described the possession of a non verbal cognitive style. The aim of this paper was to assess the genuineness of a case of phoneme color synesthesia (VA) by evaluating the influence of several psycholinguistic levels with different stimuli (isolated vowels, nonsense syllables, and words). Results demonstrate the robustness of the synesthesia no matter what the type of stimuli. To explore how this form of synesthesia manifested itself in everyday conversation, interviews were also conducted. VA reported that, in the context of conversation, phonemes still evoked colors that she had to translate in order to access the meaning. She also reported that her mental representations were multisensorial and that the verbal dimension was almost non-existent. We address several implications of this phoneme color synesthesia: the atypical speech perception that it implies, the cognitive cost of this stable system, and its relation to a specific cognitive functioning.