What would you think someone would say to you if you told them that you saw numbers as colours? For example, that you see the number three as purple? On being told she was weird because she said her “numbers were colours”, one teenager didn’t mention it again, to anyone, for the next 25 years.1 However, in an editorial in the BMJ, US expert Eagleman says that synaesthesia — where stimulation of one area of the brain triggers an anomalous perceptual experience in another (usually separated) area of the brain — is a harmless neurological condition experienced by about 1% of the population.2 He describes synaesthesia as a fusion of different sensory perceptions: “the feel of sandpaper might evoke an F sharp, a symphony might be experienced in blues and golds, or the concept of February might be experienced above the right shoulder”. Synaesthetic experiences are not hallucinations; and synaesthetic perceptions are involuntary, automatic, and consistent over time, he said. The condition may have a genetic basis.
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