Research results show that people with 'Aphantasia' who cannot visualize images in their heads can understand by looking at them.

'Aphantasia ' is a state in which it is not possible to connect images of people and landscapes as images in the head, and it is thought that there is a problem with memory, and it is said that there is no fear in ghost stories. A lot of research is being done. On the other hand, whether or not it is Aphantasia could only be identified on a self-reported experience basis, but in a paper published at the end of March 2022 by researchers at the University of New South Wales (UNSW) in Australia, Aphantasia It has been shown that people can be detected by looking at the pupillary response of the eye.

The pupillary light response as a physiological index of aphantasia, sensory and phenomenological imagery strength | eLife
https://elifesciences.org/articles/72484

The Eyes Can Reveal if Someone Has Aphantasia – An Absence of Visuals in Their Mind
https://www.sciencealert.com/the-eyes-can-reveal-if-someone-has-aphantasia-an-absence-of-visuals-in-their-mind

Aphantasia, the first description of which was first described in 1880, began full-scale research at the University of Exeter in 2005, and was given the name 'Aphantasia' in 2015. There are more people in the brain who can't think of an image than expected, and one in fifty is thought to be Aphantasia.

What is 'Aphantasia' that you can't imagine people and landscapes in your head? --GIGAZINE

by Alice Popkorn

The main reason why Aphantasia's research has not been active is that 'the state in which the image cannot be visualized in the brain' is not visible from the outside, and if it is congenital, it is abnormal in the first place. There are many cases that you do not notice. Therefore, UNSW researchers focused on the contraction and expansion of the pupil when humans perceive things firmly, and hypothesized that imaginative skills correspond to the pupil response.

In the experiment, they were divided into 'a group of 42 people with general visual imagination' and 'a group of 18 people with awareness of Aphantasia' by self-report, and each showed 'a bright triangle and a dark triangle on a gray background'. I did. After that, the screen will display a blank screen for 8 seconds, reminiscent of the image you just saw.

When this 'remembering the shape you saw just before and imagining it in your brain' was done with your eyes open, the group who declared that they had general visual imagination responded that their pupils opened according to their imagination. On the other hand, the group who was aware of Aphantasia did not see any clear change in their pupils. In the paper, the brighter and stronger the image in the brain, the larger the pupil reaction, and conversely, in the case of Aphantasia, the pupil reaction becomes extremely small in the case of Aphantasia, and the cognitive load is the pupil. We conclude that it affects size.

It is thought that the reason why the mental image and the pupillary reaction are related is that it is a by-product of the activity of the midbrain and that the eye movement when generating the image from the memory is related. Elucidation of a more detailed mechanism is an issue for the future.