Hard to Imagine

What is the stimulus of the eyes? The answer to this seemingly simple question may be more complex than it initially appears. Researchers at the University of New South Wales (UNSW) School of Psychology in Kensington, Australia, have investigated the connection, or lack thereof, between the mind’s eye and the body’s physiological response in people with aphantasia – the inability to picture images within one’s mind.

“When we visualize a beach, most of us have the experience of ‘seeing’ that image in our mind; however, a small proportion of individuals report that they do not see anything when they imagine,” study author Rebecca Keogh explains. “To date, aphantasia identification has relied purely on self-reports. We have been doing a lot of research into visual imagery and aphantasia over the past few years and have been trying to develop better ways to measure visual imagery ability without relying on self-reports, such as questionnaires.”

Building on work by Bruno Laeng and colleagues, who showed that the pupillary light response observed when we imagine pictures of differing brightness is the same, although to a lesser degree, as when physically seeing those images (1), the UNSW researchers found that reported imaginary strength correlated with the magnitude of the pupillary light response observed. They also found that aphantasic individuals, who report a lack of imagery, display no pupil change in response to attempting visualization (2). This is the first objective, physiological measure of aphantasia, and it highlights the fact that pupil responses can be driven by mental processes as well as external stimuli.

What’s next for the UNSW research team? “We hope to extend this research by looking at whether we get similar effects when people imagine complex images, such as scenes. So far, our visual imagery measurements have used visualization of basic shapes (such as triangles in the pupillometry study and gabor patches in our binocular rivalry study). If we could develop a measure of how vividly someone can imagine a complex scene, this would allow for one of the first objective measures of scene imagery,” says Keogh. “We are also aiming to modify this study to see if we can use web cameras to measure the size of the pupil, so that people can measure their own ability to visualize (or, in the case of aphantasia, inability to visualize) at home.”