Horizon: Derek Tastes of Earwax

This fascinating documentary explores the mysterious condition of synaesthesia, an extremely rare affliction where senses become linked. We meet James, who runs a pub and tastes earwax whenever he hears the name of Derek, one of his regulars; and in another case, John sees words as colours - even though he's blind. For years scientists dismissed it, but now synaesthesia is sparking a revolution in our understanding of the human mind.