Imagine walking on a beach and then gazing over the horizon as the Sun rises. How clear is the image that springs to mind? Most people can readily conjure images inside their head. But scientists have described a condition, aphantasia, in which some people are unable to visualise mental images.
Niel Kenmuir, from Lancaster, has always had a blind mind’s eye. He knew he was different even in childhood. "My stepfather, when I couldn’t sleep, told me to count sheep, and he explained what he meant, I tried to do it and I couldn’t," he says.
"I couldn’t see any sheep jumping over fences, there was nothing to count." Our memories are often tied up in images, think back to a wedding or first day at school. As a result, Niel admits, some aspects of his memory are "terrible", but he is very good at remembering facts.
And, like others with aphantasia, he struggles to recognise faces. Yet he does not see aphantasia as a disability, but simply a different way of experiencing life.