THE word “synaesthesia” derives from the phrase “joining of the senses”, but the phenomenon might not be the uncontrollable perceptual mishmash that this implies. Instead, the condition may be the result of a special ability in the “higher” brain areas used for language and attention. […]
Ward’s explanation is that colours don’t “pop out” at synaesthetes automatically. Instead, they only see numbers in colour if they fall within their focus of attention. So when volunteers happened to aim their attention at the part of the display in which the shape was hidden, he reasons, they found it quickly, but when their focus captured none, or just a portion, of the shape, they performed no better than controls (see diagram). If Ward is right, this implies that higher aspects of the brain are unusual in synaesthesia, not just those involved in automatic perception.
(via Atom Jack)