Because we live our lives entirely in our own heads, understanding the contents of someone else’s — and how radically their experience might differ from our own — is hard. New research, though, is revealing just how diverse the human imagination can be.

Take the concept of a “mind’s eye”. You might take being able to conjure up mental images in your imagination as a given. But research from myself and others has shown that 1 to 4 per cent of the population have aphantasia, meaning they lack wakeful visual imagery – ask them to “see” a hippo floating down a river on a pink lilo, and nothing happens. (Most people with aphantasia experience visual imagery in their dreams, however.)

Living with aphantasia

Aphantasia is often associated with a “thinner” than usual memory for personal past or autobiographical events, and sometimes with autism and difficulties with face recognition. People with aphantasia are more likely than those with exceptionally vivid imagery to work in STEM areas. They often report that close relatives are also aphantasic, hinting at a genetic basis. Aphantasia may be protective in some ways, possibly offering some defence against medical conditions involving imagery, like post-traumatic stress disorder (PTSD).

Fully understanding the brain signatures of aphantasia is a work in progress, but five papers published this year and last have begun to help us untangle what is going on. One brain-imaging study, for example, has shown how the regions associated with visual imagery do fire in those with aphantasia, but slightly differently, with less connectivity between the parts that deal with thought and vision.

What is hyperphantasia?

Hyperphantasia, the…