What is face pareidolia?

"Most people think you have to be mentally abnormal to see these types of images, so individuals reporting this phenomenon are often ridiculed," said lead researcher Professor Kang Lee of the University of Toronto's Eric Jackman Institute of Child Study.

"But our findings suggest that it's common for people to see non-existent features because human brains are uniquely wired to recognise faces, so that even when there's only a slight suggestion of facial features the brain automatically interprets it as a face," said Lee.

In the first study of its kind, researchers studied brain scans and behavioural responses to individuals seeing faces and letters in different patterns.

They discovered face pareidolia isn't due to a brain anomaly or imagination but is caused by the combined work of the frontal cortex which helps generate expectations and sends signals to the posterior visual cortex to enhance the interpretation stimuli from the outside world.

Researchers also found that people can be led to see different images - such as faces or words or letters - depending on what they expect to see, which in turn activates specific parts of the brain that process such images.

Seeing 'Jesus in toast' reflects our brain's normal functioning and the active role that the frontal cortex plays in visual perception, researchers said.

Instead of the phrase 'seeing is believing' the results suggest that 'believing is seeing', they said.

The study included researchers from the University of Toronto, Beijing Jiaotong University, Xidian University, and the Institute of Automation Chinese Academy of Sciences.

The findings were published in the journal Cortex.