Have you ever seen a famous face burnt into your breakfast toast? Or a potato chip that looks uncannily like your favourite in-law?

If you have, don’t worry — you aren’t crazy and you certainly are not alone.

According to new research from an international team of psychologists and published Tuesday in the journal Cortex, seeing non-existent faces in inanimate objects is “perfectly normal” behaviour.

INTERACTIVE | Map of the human brain

The phenomenon, known as ‘face pareidolia,’ is due to an interaction between two distinct parts of the brain responsible for visual perception, says Kang Lee, professor at the Dr. Erick Jackman Institute of Child Study at the University of Toronto and lead author of the research.

Face pareidolia itself has been known for centuries, but the underlying brain mechanisms were largely a mystery until now.

“We tend to think of visual perception of faces as a bottom up process: we see a face and then our brains interpret that information,” says Lee.

“But what we have shown is that a lot of what we see and perceive is actually determined by biases that already exist in our brains before any external stimuli is actually processed by the brain.”

Face pareidolia is so common that numerous websites have popped up encouraging people to post photos of their celebrities-in-toast sightings. This image comes from grilledcheeseJesus.com. (Courtesy of grilledcheesejesus.com)

Along with colleagues at several neurology institutions in Asia, Lee and his team hooked up 20 different people to a brain-scanning MRI machine and showed them random computer-generated images.

Some participants were told beforehand, however, that half of the images they would see contained a face, while another group was told half of the images would contain a letter from the English alphabet.

In both cases — faces or letters — the people saw an illusory image about 35 per cent of the time. In other words, when they expected to see something, they often did.

“The images they saw were totally random, but because they wanted to see a face, then certain random pixels in the images got picked up by the brain and interpreted as facial features or in the case of the letters, as features that resemble a letter,” says Lee.

Healthy brain function

Two regions of the brain were particularly active when participants thought they were seeing a face: the frontal cortex, which generates “expectations” about an object the brain perceives, and the posterior visual cortex, which actively processes the visuals our eyes are seeing.

“So we sometimes see things that aren’t there, but that does not mean we’re going crazy,” says Lee.

“It’s simply a reflection of the tremendous power that our brains have and how it essentially imposes itself on the outside world, rather than the other way around.”

According to Lee, people will often see religious figures, like Jesus or the Virgin Mary, burnt into toast or drawn in the clouds because religious beliefs can strongly influence the world we “want to perceive.”

“Our findings suggest that it’s common for people to see non-existent features because human brains are uniquely wired to recognize faces. Even when there’s only a slight suggestion of facial features, the brain automatically interprets it as a face.”