Hearing words and seeing colours: an experimental investigation of a case of synaesthesia.

A case of 'chromatic-lexical' (colour-word) synaesthesia is described, and its genuineness confirmed using the criterion of stable cross-modality imagery across time. The synaesthesia could not be accounted for by a memory hypothesis, nor was it associated with any psychiatric condition. Further analysis did not identify any semantic relationship between real words and colours, but the colours of nonwords were determined by the colours of the individual letters. Numbers also had their own stable colours. The experience of synaesthesia was triggered by other auditory stimuli, but most strongly by words. Cortical electrophysiological recording failed to reveal any abnormalities. An unusual organisation of modalities in the brain is postulated to account for the phenomenon.