Scientists Develop Objective Test for Aphantasia, the Inability to Visualize
Table of Contents
A groundbreaking new study offers the first biological evidence for aphantasia, a neurological condition affecting an estimated 1-4% of the global population – roughly 82 to 380 million people – and provides an objective test to measure the vividness of mental imagery.
The challenge of understanding consciousness and individual differences in perception has long been hampered by the subjective nature of internal experience. Its difficult to work out what is going on in your own mind, let alone anyone else’s, and this is notably true for those with aphantasia, who may not even realize their minds function differently. The Aphantasia Network defines the condition as the inability to voluntarily visualize mental images, impacting how individuals think and remember.
Researchers at UNSW sydney developed a novel test to identify aphantasia, moving beyond self-reporting. The study, published in eLife, utilized eye-tracking technology to measure pupil responses as participants visualized shapes.
Pupil Dilation Reveals the Secrets of the Mind’s Eye
The research team initially recruited 42 participants who reported having a visual creativity. These individuals wore glasses that tracked their eye movements and pupil size while viewing bright and dark shapes against a gray background. As was to be expected,pupils constricted in response to bright shapes and dilated in response to darker ones – a normal physiological reaction.
Participants were then asked to imagine those same shapes and rate the vividness of their mental images. Researchers found that pupil dilation and constriction mirrored the responses to the physical stimuli,with more vivid imagery correlating to stronger pupillary changes. “This really is the first biological, objective test for imagery vividness,” stated a senior author of the study. “the pupillary reflex is an adaption that optimises the amount of light hitting the retina, and we were surprised to see more dramatic changes in those reporting more vivid imagery.”
Aphantasia Revealed Through objective Measurement
The team then recruited 18 participants who self-identified as having aphantasia. these individuals exhibited typical pupil responses to the actual bright and dark shapes.However, when asked to visualize the shapes without a physical stimulus, their pupils did not substantially dilate or constrict.
“One of the problems with many existing methods to measure imagery is that they are subjective,” explained a researcher.”Our results show an exciting new objective method to measure visual imagery, and the first physiological evidence of aphantasia.” The findings suggest a potential for a future “blood test” equivalent for identifying the condition, impacting an estimated 1.3 million Australians and 400 million people worldwide.
Further testing revealed an interesting nuance: participants with aphantasia did exhibit pupil dilation when asked to imagine four objects concurrently.This suggests increased mental effort, and confirmed that the initial lack of response wasn’t due to a lack of engagement. “Our pupils are known to get larger when we are doing a more difficult task,” explained a PhD candidate involved in the research. “Imagining four objects simultaneously is more difficult than imagining just one.This indicated that the participants with aphantasia were indeed trying to imagine in this experiment, just not in a visual way.”
Memory and the varied Human Mind
The study also addressed common misconceptions about aphantasia and memory. While individuals without aphantasia may rely on imagery to recall events, the absence of vivid mental pictures doesn’t necessarily equate to a poorer memory. “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,” noted a co-author on the paper.
These findings underscore the remarkable diversity of the human mind. “These findings further highlight the wide variability of the human mind that can frequently enough remain hidden until we ask someone about their internal experiences or invent new ways to measure the mind,” the researcher added. “it reminds us that just because I remember or visualise something one way, doesn’t mean everyone does.”
