Synaesthesia is a condition in which a stimulus in one sensory modality automatically triggers a perceptual experience in another. For example, on hearing a sound, the person immediately sees a colour. How does this happen? Is it a real phenomenon? Why do some people develop this condition and not others? And might synaesthesia provide important clues about the organization of the normal brain? This volume brings together what is known about this fascinating neurological condition. The above questions, and new issues arising from the recent wave of cognitive neuroscientific research into synaesthesia, are debated in a series of chapters by leading authorities in the field. The book will be of great interest to researchers and students in the cognitive neurosciences, and is intended to spark further investigation into this relatively neglected, extraordinary phenomenon.