LivingDo you suffer from aphantasy? Your eyes can give...

Do you suffer from aphantasy? Your eyes can give it away

Aphantasy is a strange condition that makes people who suffer from it unable to visualize images in their minds . A group of Australian researchers has found a way to identify it by looking at our eyes and more specifically at the pupils.

When the human eye is exposed to bright light, the pupils constrict, and when exposed to darkness they expand to let more light through to the retina. In addition, our pupils can change in size depending on the cognitive tasks that we are performing.

The scientists behind the study that has been published in eLife examined two groups of participants. One of the groups was made up of 42 people with a capacity for regular visual imagination, and the other group of 18 people with self-reported afantasy. Everyone was asked to see images with light and dark shapes on a gray background. Individuals in both groups showed regular pupil dilation responses to light and dark images.

The researchers then asked both groups to imagine the same images with their eyes open. Interestingly, they found that the pupils of individuals with regular visual imagery continued to contract and expand, while the pupils of individuals with afantasy did not change size significantly.

“Our results provide novel evidence that our pupils respond to the vividness and strength of a visual image held in mind; the stronger and more vivid that image, the greater the pupillary light response r,” say the study’s authors. . “Finally, we show that, overall, there is no evidence for this pupillary response in individuals without mental imagery (aphantasy),” they add.

Since the pupil’s response to light is involuntary, the study offers a new unbiased measure of aphantasy, since this technique is not based on self-report, that is, on what the individual declares.

“We are now close to an objective physiological test , like a blood test, to see if someone really has it,” says the study’s lead author, psychologist Joel Pearson of the University of New South Wales (UNSW, in his acronym in English), in Sydney.

In addition, the researchers found that people who could imagine more vivid images showed greater pupil dilation . This is one more tool that researchers can use to measure the strength of mental images in future studies.

One of the most relevant points raised in the study is how mental images can drive the involuntary response of the pupils.

One of the interpretations proposed by the authors has to do with shared top-down mechanisms between visual images and perception, in which brain regions that interpret visual information process imaginary images in the same way as actual visual data. In this case, the pupil responds to imagined luminance in a similar way to how it responds to retinal-based light sources, supporting the conclusions that the stronger or more vivid the mental images, the more “perception-like”. “will be.

The researchers also wanted to make sure that the participants with afantasy were actually trying to imagine the images in the study, so they included an additional task, in which they were asked to visualize four shapes simultaneously, instead of one.

“Our pupils are known to enlarge when we perform a more difficult task,” says neuroscience researcher Lachlan Kay of UNSW’s Future Minds Laboratory. “Imagining four objects simultaneously is more difficult than imagining just one. People with afantasy’s pupils dilated when they imagined four shapes compared to one, but did not change depending on whether the shapes were bright or dark,” he said.

The ability that we humans have to form mental images of visual content helps many of the important functions that our brain can perform. We do this to retrieve information from our long and short term memory , when we imagine letters and symbols when we are learning a language or when we navigate or remember where we have been.

For people with aphantasy, the mental world is different, highlighting the truly diverse neurological ways we all interact with the world.

 

Reference:

Lachlan, K et al. 2022. he pupillary light response as a physiological index of aphantasia, sensory and phenomenological imagery strength. eLife. DOI: 10.7554/eLife.72484

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