 Imagine if every time you saw someone called Derek you got a strong taste of earwax in your mouth. It happens to James Wannerton, who runs a pub. Derek is one of his regulars. Another regular s name gives him the taste of wet nappies. For some puzzling reason, James s sense of sound and taste are intermingled. Dorothy Latham sees words as colours. Whenever she reads a black and white text, she sees each letter tinged in the shade of her own multi-coloured alphabet - even though she knows the reality of the text is black and white. Spoken words have an even stranger effect. She sees them, spelled out letter by letter, on a colourful tickertape in front of her head. Both James and Dorothy have a mysterious condition called synaesthesia, in which their senses have become linked. For years scientists dismissed it, putting it in the same category as séances and spoon-bending. But now, synaesthesia is sparking a revolution in our understanding of the human mind.