Seeing or tasting sounds, hearing colours, being touched by sights… Alyosha was about 9 years old when he tried to account for a panic attack by saying: “I was scared. I saw a yellow ‘z-z-z’ sound.” This was confusing, until I realised he had synaesthesia. Synaesthesia (Greek syn – ‘together’ and aesthesis – ‘perception’) or ‘cross-sensory perception’ is an involuntary physical experience when the stimulation of one sensory modality triggers a perception in one or more diffe