'IT WAS ONLY recently that I learnt about aphantasia, a condition in which people cannot conjure up or visualise mental imagery. A friend explained that if she asked her children to imagine seeing an apple, they could describe exactly what they saw in their mind’s eye. She, on the other hand, could think about an apple, but could not bring an image – of an apple purchased, an apple eaten, an apple in a picture – to mind.' (Introduction)