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And up to 6% of people may experience some degree of aphantasia.

Prof Zeman says 17,000 people have contacted him in the past decade, with experiences of aphantasia and hyperphantasia.

But in those with aphantasia, that process can break down at any point.

And aphantasia can have benefits.

Lots of question remain about aphantasia and hyperphantasia, such as what are the different sub-types and why it might be a genetic thing.