MYSTERIES OF SCIENCE

Discover the truth behind the strange effect called pareidolia.

Investigate a phenomenon that tricks everyone.

Have you ever looked up at clouds on a summer’s day and seen a face looking back at you? Or spotted the “man in the moon” smiling down at you at night? Or noticed eyes and a smile on the front of a car? If you have, you’re not alone. The name for this phenomenon – our ability to see meaningful images in random places or things – is pareidolia, (pronounced par-i-doh-lee-ah). Seeing faces in everyday objects is one of its most common forms.

A mysterious sickness?

Pareidolia has been known about for thousands of years and for a long time it was thought to be a symptom of mental illness. In William Shakespeare’s play Hamlet, written in around 1601, the prince of Denmark (who is believed to be going mad by some of the other characters) sees clouds in the shapes of camels and weasels. However, artist Leonardo da Vinci, who died in 1519, found the effect very useful. “If you look at any wall spotted with various stains,” he wrote, “you will be able to see in it a resemblance to various different landscapes.” Da Vinci is one of several artists who used pareidolia to conceal “hidden” objects in his paintings – for instance, faces that appear when seen from a certain angle.

Why do people see faces?

Several theories have tried to explain pareidolia. One is that people’s skill at recognising faces develops from such a young age that the human brain sometimes reacts to faces when there are none. The American scientist Carl Sagan suggested in 1995 that pareidolia is a result of evolution. “Those infants who a million years ago were unable to recognise a face smiled back less,” he wrote, and so “were less likely to win the heart of their parents.”

Others have said that it is a survival mechanism. The lives of our ancestors often depended on distinguishing quickly between friends and enemies, so our brains adapted to detect faces everywhere. In 2012, Finnish scientist Tapani Riekki and his colleagues found that people with a belief in religion or the supernatural are more likely to see patterns in random information.

The mind’s eye

In 2014, Dr Kang Lee, a scientist at the University of Toronto in Canada who studies how young people’s brains work, proposed a different theory. He said that rather than the eyes spotting a face-like pattern and communicating that information back to the brain, the brain, in fact, imagines a face and “tells” the eyes to see it. Dr Lee scanned the people’s brains while showing them a series of grainy images, some of which contained hidden faces. He then asked the participants “Do you see a face?”. Once they were asked the question, people answered yes 34% of the time, even if there was no face. What’s more, if participants reported seeing a face, the visual cortex of their brain – the part of the brain that processes information from the eyes – lit up. Dr Lee concluded that “a lot of things we see in the world aren’t coming from our sight but are coming from inside our minds.”

Computers also do it

It’s not just humans who see faces where they are none – machines do it too. The facial-recognition software used by many devices and apps is a genius invention but sometimes computers get it wrong. In this case, though, it’s nothing to do with evolution or the imaginings of a computer’s brain. Instead it’s a result of how the system has been trained to interpret certain shapes and data points.

Now that you know some of the tricks your mind can play, why not take another look up at the clouds and see what you can find? Perhaps a camel or a weasel will emerge, or maybe you will see someone you know. And who knows? Maybe you’ll come up with a whole new theory as to why that face is there.

Do you see a spooky face?