Like Chicago, Athens, Dubai, Cairo, Shanghai and some 40 other cities around the world, Montreal is now home to its own Museum of Illusions, which opened Saturday at 44 Saint-Antoine Street West.

On display is a wide range of illusions and mirages, some classic and some never seen before. All are designed to instill doubt in our minds momentarily.

"An illusion is the meeting point between what we think we know well and an effect of surprise," explains museum staff member Ines Nozica.

How can we fool our brains so easily?

According to a professor in the University of Montreal's biological sciences department, an optical illusion occurs when there is a discrepancy between information captured by our eyes and our brain's interpretation of it.

"There's a conflict between what we expect and what we're confronted with," said Stéphane Molotchnikoff.

Jocelyn Faubert, professor at the university's school of optometry, explains: "When we explore the world, all we see are clichés. Our eyes are moving and exploring all the time, they're two-dimensional snapshots that we see continuously on our retina, but our brain interprets it all in a fluid way."

Illusions play with light refraction, perspective or colour, among other things, to simulate movement or trick our brain, which is simply trying to interpret what it's presented with based on what it knows in reality, Faubert explains.

"That's what's fascinating: once you pay attention and observe properly, you can see that there's something impossible in the image in relation to physical reality," he notes.


Not all illusions can be observed by everyone, and not everyone has the ability to perceive illusions, say the scientists.

"Some people are less able to perceive certain illusions than others," admits Faubert.

"In illusions with two images, some people can switch from one image to the other, while others will never be able to see a second. We don't have a clear explanation at the moment, apart from the fact that it demonstrates that there are differences in our respective constructions of reality."

Illusions can also be used for clinical purposes: "Someone who has received a blow to the head is said to see stars because there has been a shock to neurons that make them see something, even if it's not present in the retina," illustrates Molotchnikoff.

"Someone with a vascular lesion can also experience an activation of neurological connections that create an illusion.'

The reverse is also true, says the researcher.

"What's interesting for the scientist is to study the strategies the brain uses to perceive, but also the shortcuts it makes to interpret our environment correctly," adds Faubert.

"Because once the brain has realized that it has been 'deceived,' it corrects the information to perceive it in accordance with reality, which is why we sometimes no longer perceive the illusion," says Molotchnikoff. "In a way, it resets the counter to zero."

Since the brain is "very plastic," it can be trained to detect illusions more easily.

"You can train it to pay attention to certain elements," says Faubert. "If you tell someone to look at certain details, they may finally see the illusion, effects they haven't seen before."


This report by The Canadian Press was written with the financial assistance of the Meta Exchange and The Canadian Press for news. It was first published in French on June 10, 2023.