HMN 2026: What an illusion involving a fake hand can tell us about our mind–body connection

People who have a weaker sense of self are also more likely to have less bodily awareness, McGill researchers have found. The study supports the idea that people’s perceptions of themselves and how they experience their own bodies are deeply connected. Beyond deepening psychologists’ understanding of “embodied cognition,” the connection between our minds and our fundamental bodily awareness, the findings could have concrete applications regarding the treatment of certain psychiatric conditions, the researchers said.

A more malleable self?

This study replicated and confirmed the results of a smaller 2019 study previously led by Sonia A. Krol, who is also a co-author of the current study, published in the Canadian Journal of Experimental Psychology / Revue canadienne de psychologie expérimentale. It involved 77 participants ages 18-40 from the McGill community, who were subjected to a commonly used device in psychological research called the “rubber hand illusion.”

One of a participant’s hands was hidden behind a screen, while a rubber hand was placed in view. Both the subject’s hand and the fake hand were wearing a glove to hide any differences in skin tone. Researchers then used a paintbrush to stroke the hand of the subject and the fake hand in two different ways: in sync and out of sync.

While it was expected that subjects would report feeling like the rubber hand was theirs when the hands were stroked simultaneously—and this was generally the case—some people also experienced confusion when the strokes were not simultaneous, said Jennifer Bartz, senior author of the study, Professor in the Department of Psychology, and Director of the McGill Laboratory of Attachment and Prosociality.

The participants who were more vulnerable to the illusion tended, in the accompanying questionnaire, to score lower on a scale measuring the clarity, coherence, and stability of their sense of self.

“This really suggests that they maybe have a more malleable kind of bodily self, where they’re more vulnerable to incorporating other things in the environment into their sense of self, even when most people wouldn’t be vulnerable to that,” said Bartz.

How two understandings of the self go ‘hand in hand’

Embodied cognition makes sense from an evolutionary standpoint but has not often been researched in an empirical way, said Willis Klein, lead author of the study and Ph.D. candidate in the Department of Psychology.

“To be able to take this beautiful theoretical framework and to say, here’s experimental evidence for this quite intuitive perspective on what the mind is, it’s just amazing,” he added.

The researchers said the results raise interesting questions for future research, such as how embodied cognition can play out in processes like empathy, or how clinicians can better help people presenting with a less stable sense of self, such as individuals living with borderline personality disorder.

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