When Blake Ross read a New York Times piece on the mystery of a man who lost his ability to form mental images, he was shocked.
But Ross was not disturbed by the strangeness of such an unfortunate case.
Instead, as Ross wrote on Facebook, he thought:
What do you mean 'lost' his ability?
... Shouldn’t we be amazed he ever had that ability?
It turns out that Ross has Aphantasia and never knew it.
This means he is unable to visualise mental images - in other words, his mind's eye is blind.
If they are told to imagine a sunset over a beach or a horse running through a field, most people can conjure some sort of image.
We vary in how rich our visual imagery is: for some, the picture will appear as easily and as detailed as a photograph; for others, it will be fleeting, even cartoonish.
But people with Aphantasia can conjure nothing at all.
If there are asked to imagine a friend's face, they will be able to reel off their hair or eye colour, but will no be able to actually picture anything.
This even applies to dreams and conjuring someone's voice.
I’ve had a couple dreams but there was no visual or sensory component to them.
When I woke up, I just knew a list of 'plot points' about things that happened.
This is also how I digest fiction.
He also said:
I can’t read this in Morgan Freeman’s voice, nor can I 'hear' the theme song to Star Wars in any sort of 'mind’s ear'.
Though people with Aphantasia have memories, they are not visual, but a list of facts.
Are aphantisic individuals really 'mind blind' or are they in fact not conscious of their mental images?
A study used 'binocular rivalry' - where perception flips between two images, one presented to each eye - to assess visual imagery objectively.
Participants wore 3D red-green glasses with images super-imposed onto them, which stops the brain seeing both images at once.
When the average person is asked to imagine the 'green' image beforehand, they are far more likely to see the green image after putting on the 3D glasses.
The stronger their visual imagery, the more they often will see the 'green image'.
Over almost 100 trials, it was found that when Aphantasics tried to form a mental image, it had no effect on what they saw with the glasses on.
This suggests that people with Aphantasia really have no visual imagery.
Why some people are mind blind
Current theories suggest we reactivate the same pattern of activity - a network that spans from the frontal cortex to the visual areas at the back of the brain - each time we picture something.
It might be that aphantasic individuals use a different network completely when they attempt tasks involving visual imagery or are not able to reactivate these patterns.