The former president of Pixar and Walt Disney Animation Studios says he has a "blind mind's eye". Ed Catmull, 74, has the condition aphantasia, in which people cannot visualise mental images at all. And in a surprising survey of his former employees, so do some of the world's best animators. (BBC)

Aphantasia, a term coined by Adam Zeman, a neurologist and professor of cognitive and behavioural neurology at Exeter University Medical School, describes people who are unable to visualise. It affects some 2 to 3 per cent of the population, or around 2million people in the UK. (Daily Mail)