Most people can picture images in their heads – the look of an apple, the appearance of their kitchen or the smile of their best friend – but not everyone can.
Those who cannot visualise anything in their mind’s eye are probably among 1% of people with extreme aphantasia, according to a review of studies on the phenomenon.
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It is not a disorder and does not imply a lack of imagination but can have subtle effects on everyday life, says Prof Adam Zeman, honorary professor of neurology at the University of Exeter, who came up with the term nearly 10 years ago.
Differences in connectivity between regions of the brain may explain why, Prof Zeman says.
Asked to picture an apple, for example, most people go through a succession of steps, including nudging the brain to remember what an apple looks like and activating the brain to create an image of it.
But in those with aphantasia, that process can break down at any point.
“Thoughts remain thoughts,” Prof Zeman says, “whereas for others, thought translates into sensory terms.”
While aphantasics think about memories, other people are able to recollect and live those memories.
But intriguingly, many aphantasics can visualise images while dreaming – probably because it is a more spontaneous task beginning deep down in the brain, Prof Zeman says.
