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.

They are also less likely to recognise faces, remember the sound of a piece of music or the feel of sandpaper, and more likely to work in science, maths or computing.

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

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.