If you have seen The Little Mermaid, you can probably visualise Ariel in your mind’s eye, but for Glen Keane, the Disney animator who drew her, that is impossible. Keane has a condition called aphantasia, meaning his mind’s eye is blind. And so does Ed Catmull, the former president of Pixar and Walt Disney Animation Studios.

Catmull, 74, told the BBC that he discovered his condition while attempting to visualise a sphere during a session of Tibetan meditation: “I went home, closed my eyes … I couldn’t see a thing,” he said. “For an entire week, I kept trying to visualise this sphere.”

Aphantasia is a relatively unknown – and only recently discovered – condition that affects 2% of the population, and both genders equally, says Adam Zeman, professor of cognitive and behavioural neurology at the University of Exeter. “People with aphantasia can think about an apple, or a front door or a loved one perfectly well, but they just can’t bring to mind the visual image of that thing or person.”

In some people, aphantasia not only leaves them without any visual imagery, but they have no sensory recall at all. Alan Kendle, an engineer and the author of Aphantasia: Experiences, Perceptions and Insights, says he cannot recreate any of his five senses in his mind. “I can’t hear anything in my head unless it comes through my ears. I’ve got no inner voice. It’s absolute silence in there.”

Kendle, 57, has difficulty recognising people if he hasn’t seen them for a few months, and can sometimes struggle with travelling to unfamiliar places – and, despite being a film fan, is unable to daydream about his favourite cinematic spectacles. “I went to watch Interstellar at the BFI in London. It was amazing to see it on the big screen – but as soon as I’d left I couldn’t picture it,” he says.

The thought of not being able to conjure mental images may seem distressing for those who can, but Zeman says that most aphantasiacs are not “desperately upset” when they discover their condition, “partly because they’ve always been that way”. One potentially upsetting aspect is the inability to recall a loved one’s face, especially one who has died. “It can be a source of regret,” says Zeman.

Catmull told the BBC that aphantasia was not a barrier to creativity, pointing out that Keane’s work was proof that you do not have to be able to picture something to be able to draw it. “People had conflated visualisation with creativity and imagination, and one of the messages is: ‘They’re not the same thing.’”