Lead researcher Prof. Kang Lee of the University of Toronto's Eric Jackman Institute of Child Study, said most people think you have to be mentally abnormal to see these types of images, so individuals reporting this phenomenon are often ridiculed.
He said their findings suggest that it's common for people to see non-existent features because human brains are uniquely wired to recognize faces, so that even when there's only a slight suggestion of facial features the brain automatically interprets it as a face.
They discovered face paredilia 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. Instead of the phrase "seeing is believing" the results suggest that "believing is seeing."
The findings have been published in the journal Cortex.