Most people are familiar with mental imagery: picturing a scene from a novel, mentally rehearsing a presentation or imagining an upcoming birthday party, for example.
Yet, according to a by 91亚色 Associate Professor Kevin Lande, one of the mind's most familiar experiences remains a scientific mystery.
In a paper published in Psychological Review, Lande and co-author E.J. Green of Johns Hopkins University ask: "What role does mental imagery play in the mind?" They challenge a growing view that imagery is critical to much of perception and cognition.
Some contemporary theories propose that mental imagery is an ingredient of everything from memory and decision-making to perception. One argument, notes Lande, suggests what people perceive is often shaped by mental imagery.
For example, when part of an object is obscured from view, the brain automatically fills in the missing details 鈥 a process that a growing number of philosophers, psychologists and neuroscientists suggest is a form of mental imagery rather than direct perception.
"If most of our visual experiences involve some amount of 'filling in,' then much of what we seem to see is, in fact, imaged," says Lande.
However, as the concept of mental imagery is expanded to include a wider range of neural processes, Lande says it becomes more challenging to define a theory on mental imagery. The authors argue there is very little that connects ordinary experiences of mental imagery to the processes involved in filling in missing details.
鈥淢any want to say that visual imagery, for example, is just perceptual processing that does not depend directly on the light that hits the eye,鈥 Lande says. 鈥淚f that鈥檚 right, then it turns out that all sorts of things seem to require imagery. But when you look at the scientific research on these different processes, you find that they all function very differently.鈥
To count 鈥渇illing in" as imagery, Lande says, one must adopt a really thin conception of imagery 鈥 which doesn鈥檛 help with making new predictions and explanations.
The study also draws on recent research on people with aphantasia 鈥 a condition in which people report little or no conscious mental imagery 鈥 which shows they often perform as well as people who experience vivid mental imagery. This evidence, notes Lande, challenges assumptions about the role imagery plays in everyday thinking and cognition.
For example, a person can navigate Toronto by vividly imagining a map in their head. But, they can also move across the city by following habits, remembering directions or using a feeling of familiarity without ever forming a clear mental picture. If this task can be achieved with roughly equal success and speed with or without mental imagery, researchers may struggle to understand the role it plays in cognition.
Lande and Green suggest that imagery is not a critical component of perception, but argue there is a deeper issue: science lacks a clear account of what exactly imagery is.
"As researchers attribute an ever-growing range of mental activities to imagery, the concept risks becoming too broad to explain anything clearly,鈥 says Lande, a philosopher at the Faculty of Liberal Arts & Professional Studies. 鈥淚f we define mental imagery so as to encompass a diverse range of experiences and cognitive processes, researchers may find it increasingly difficult to test theories about its role in the mind.
"However, if we try to tie our theory of imagery more close to our familiar conscious experiences, the puzzle of aphantasia suggest that it plays very little role in perception and cognition."
The study highlights the value of interdisciplinary approaches to studying the mind. Drawing on philosophy, psychology and cognitive science, the authors contend that questioning basic assumptions can lead to new insights into how the mind works.
Lande, who is a Connected Minds 91亚色 Research Chair in Philosophy of Representation, says the work is closely aligned with 91亚色鈥檚 Vision: Science to Applications (VISTA) program, and the $318-million Connected Minds research initiative led by 91亚色 and Queen鈥檚 universities which focuses on bridging intelligence, technology and society. He is also affiliated with 91亚色's Centre for Vision Research and the Centre for Integrative and Applied Neuroscience.
The paper concludes that researchers may need to rethink the concept of mental imagery to get a "better picture" of how perception, memory and cognition interact.