Can you taste words, feel flavours as a shape, or hear colors? If so you may well have synaesthesia, a neurological condition that gives rise to a 'merging of the senses'. This Very Short Introduction describes synaesthesia's many forms, and delves into the underlying neuroscience. Explaining the scientific basis for synaesthesia, Julia Simner considers how we can measure the effects synaesthesia has on the everyday lives of people living with...