Windows to the soul: Pupils reveal 'aphantasia' -- the absence of visual imagination
Date:
April 20, 2022
Source:
University of New South Wales
Summary:
Picture this, if you will: Aphantasia can be detected with an
eye-opening look into our pupils.
FULL STORY ========================================================================== Visual imagination -- or rather, the lack of it -- can be verified by
measuring pupil dilation, thereby providing the first physiological
evidence of aphantasia, new research shows.
==========================================================================
The study, led by researchers from UNSW Sydney and published in eLife,
found that the pupils of people with aphantasia did not respond when asked
to imagine dark and light objects, while those withoutaphantasia did.
To first gauge the pupillary reflex of non-aphantasic people, the
researchers sought 42 study participants, self-reported as having a
visual imagination, and fitted them with glasses to track their eye
movements and pupil sizes.
Participants were then exposed to bright or dark shapes against a grey background, which predictably evoked pupillary constriction in response
to bright shapes (comparable to looking up at a bright sky) and pupillary dilation in response to dark shapes (after switching a light off).
Next, to test visual imagery -- the mind's capacity to visualise
objects - - participants were asked to simply imagine those same light
or dark shapes (with their eyes open, for their pupils to be tracked)
and subsequently report the 'vividness' of that imagery.
The researchers found that even in response to imagined bright and
dark shapes, the participants' pupils still constricted and dilated appropriately, a pupillary response that was larger in those reporting
greater imagery vividness.
==========================================================================
"The pupillary reflex is an adaption that optimises the amount of light
hitting the retina," says Professor Joel Pearson, senior author on 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 imagery. This
really is the first biological, objective test for imagery vividness."
Testing for a lack of imagination Finally, with the link between visual
imagery and pupillary response established, the researchers sought to
test the effect in aphantasic individuals. The researchers repeated the
study with 18 participants self- reporting aphantasia.
Exposing participants to bright and dark shapes, the researchers found
that aphantasic individuals exhibited the same pupillary response as
the general population: constriction to bright, dilation to dark.
However, during the study's second component where participants were asked
to visualise those same shapes, the pupillary response of aphantasic individuals did not significantly differ in response to imagined dark
versus imagined bright objects.
==========================================================================
"One of the problems with many existing methods to measure imagery is
that they are subjective, that is to say they rely on people being able
to accurately assess their own imagery. Our results show an exciting
new objective method to measure visual imagery," says Prof Pearson,
"and the first physiological evidence of aphantasia. With over 1.3
million Australians thought to have aphantasia, and 400 million more internationally, we are now close to an objective physiological test, like
a blood test, to see if someone truly has it." To ensure the aphantasic participants were really attempting imagery, the researchers included
a further experimental condition, requesting aphantasic individuals to visualise four shapes, instead of one.
While the pupils of those with aphantasia showed no difference when
imagining light versus dark objects, they did show a difference imagining
one versus four objects, suggesting more mental effort, thereby negating
an explanation of non- participation by aphantasic individuals.
"Our pupils are known to get larger when we are doing a more difficult
task," says Lachlan Kay, PhD candidate in the Future Minds Lab,
UNSW. "Imagining four objects simultaneously is more difficult than
imagining just one. The pupils of those with aphantasia dilated when
they imagined four shapes compared to one, but did not change based
on the whether the shapes were bright or dark. This indicated that
the participants with aphantasia were indeed trying to imagine in this experiment, just not in a visual way." "The aphantasic pupil response to
the four objects condition is also a really exciting finding," adds Prof Pearson, "because for the first time we have strong biological evidence
that those with aphantasia are really trying to create a mental image,
putting to rest claims that they may simply not be attempting to create
a mental image." "These findings are also really interesting in regard
to memory and aphantasia," said Dr Rebecca Keogh, Postdoctoral research
fellow 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, remembering many images for a short period
of time, without using visual imagery.
"These findings further highlight the wide 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
just because I remember or visualise something one way, doesn't mean
everyone does." What's next for aphantasia research? A look into the
future...
Next, Prof Pearson and his team at the Future Minds Lab plan to
investigate how this new method could be scaled up and run online to allow
a global, efficient and objective measurement of imagery and aphantasia.
"This really is an exciting time. We are very close to having objective, reliable tests for extreme imagery, aphantasia and hyperphantasia
(extremely strong visual imagery) that could be scaled up to run online
for millions of people everywhere," says Prof Pearson.
"We know that thinking in pictures or not affects the number of details
in lifelong memories, how emotional we get when reading, and how we hold
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."
========================================================================== Story Source: Materials provided by
University_of_New_South_Wales. Original written by Jesse Hawley. Note:
Content may be edited for style and length.
========================================================================== Journal Reference:
1. Rebecca Keogh, Lachlan Kay, Thomas Andrillon, Joel Pearson. The
pupillary
light response as a physiological index of aphantasia, sensory and
phenomenological imagery strength. eLife, 2022; 11 DOI: 10.7554/
eLife.72484 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220420092150.htm
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