Students reveal ‘aphantasia’ – the absence of visual imagination – ScienceDaily
Visual imagination – or rather the lack thereof – can be checked by measuring pupil dilation, providing the first physiological evidence for aphantasia, according to new research.
The study, conducted by researchers at UNSW Sydney and published in eLifefound that pupils of people with aphantasia did not respond when asked to imagine dark and light objects, while those without aphantasia did.
To first assess the pupillary reflex of non-aphantasic people, the researchers sought out 42 study participants, who self-reported as having visual imaginations, and fitted them with glasses to track their eye movements and pupil size.
Participants were then exposed to bright or dark shapes against a gray background, which predictably evoked pupillary constriction in response to bright shapes (comparable to looking at a bright sky) and pupillary dilation in response to dark shapes. (after turning off a light).
Then, to test visual imagery – the mind’s ability to visualize objects – participants simply had to imagine those same light or dark shapes (with their eyes open, so their pupils were tracked) and then report “vividness”. of this imagery.
The researchers found that even in response to conceived light and dark shapes, participants’ pupils were always constricted and dilated appropriately, with greater pupillary response in those reporting greater imagery vividness.
“The pupillary reflex is an adaptation that optimizes the amount of light hitting the retina,” says Professor Joel Pearson, lead author of the paper. “And while it was already known that imagined objects can evoke so-called ‘endogenous’ changes in pupil size, we were surprised to see more dramatic changes in those reporting more vivid images. truly the first biological and objective test of image vividness.”
Test of a lack of imagination
Finally, the link between visual imagery and pupillary response having been established, the researchers sought to test the effect in aphantasic individuals. The researchers repeated the study with 18 participants self-reporting aphantasia.
By exposing participants to light and dark shapes, the researchers found that aphantasic individuals exhibited the same pupillary response as the general population: constriction in light, dilation in dark.
However, during the second part of the study where participants were asked to visualize these same shapes, the pupillary response of aphantasic individuals did not differ significantly in response to imagined dark objects compared to imagined bright objects.
“One of the problems with many existing methods for measuring imagery is that they are subjective, that is, they rely on people’s ability to accurately assess their own imagery. Our results show an exciting new objective method for measuring visual imagery,” says Prof Pearson, “and the first physiological evidence of aphantasia. With over 1.3 million Australians believed to have aphantasia, and 400 million more in the world, we are now close to an objective physiological test, like a blood test, to see if someone really has it.”
To ensure that the aphantasic participants were really attempting to take images, the researchers included another experimental condition, asking the aphantasic individuals to visualize four shapes instead of one.
While pupils of those with aphantasia showed no difference when imagining light versus dark objects, they showed a difference when imagining one object versus four, suggesting more mental effort, denying thus an explanation for the non-participation of aphantasic individuals.
“Our students are known to get bigger when we perform a more difficult task,” says Lachlan Kay, PhD student at Future Minds Lab, UNSW. “Imagining four objects simultaneously is more difficult than imagining just one. The pupils of people with aphantasia dilated when imagining four shapes versus one, but did not change depending on whether the shapes were light or dark. This indicated that participants with aphantasia were indeed trying to imagine in this experiment, but not visually.”
“The aphantasy pupil’s response to the four object condition is also a really exciting finding,” adds Professor Pearson, “because for the first time we have strong biological evidence that people with aphantasia are really trying to create a mental image, putting to rest claims that maybe they’re just not trying to create a mental image.”
“These findings are also very interesting with respect to memory and aphantasia,” said Dr Rebecca Keogh, postdoctoral researcher based at Macquarie University and another author of the study. “Our previous work has shown that aphantasic individuals are able to perform visual working memory tasks, recalling many images for a short period of time, without using visual imagery.
“These findings further underscore the great variability of the human mind that can often remain hidden until we ask someone about their internal experiences or invent new ways to measure the mind. It reminds us that this Just because I remember or visualize something in a way doesn’t mean everyone else does.”
What future for research on aphantasia? A look to the future…
Next, Professor Pearson and his team at the Future Minds Lab plan to investigate how this new method could be scaled up and performed online to enable comprehensive, efficient and objective measurement of imagery and aphantasia.
“It is truly an exciting time. We are on the verge of having objective and reliable tests for extreme imagery, aphantasia and hyperphantasy (extremely strong visual imagery) that could be scaled up to online for millions of people around the world,” says Professor Pearson.
“We know that thinking in pictures or not affects the number of details in lifetime memories, how emotional we become when reading, and how we retain things in short-term memory. This new method will allow us to understand the brain mechanisms of extreme imagery and the global implications for how we think, make decisions and feel.”