Muriel still remembers when her father painted the family house.
The paint was white. But it smelled unmistakably blue. Then
there's Kristen, who tastes words, complete with texture and
temperature. Often the spelling affects the flavour. 'Lori', for
instance, tastes like a pencil eraser, but 'Laurie' tastes
lemony. These two women have synaesthesia, which means that
their senses mingle. A stimulus to one sense gives rise to
entirely unexpected responses in others. A scent, in Muriel's
case, triggers not only smell but colour. Grass might smell
purple - or roses grey. The taste of chocolate might bring on a
prickly feeling, of pins jabbing into flesh. Sounds, too, evoke
colours and shapes. One synaesthetic can picture the green loops
of a helicopter's drone; another is assaulted with red daggers
on hearing a bell. Most people with the condition - there are an
estimated one in 25 000 - simply hear ... To continue reading
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