Whether it’s the image of Jesus in a piece of toast or Adolf Hitler reincarnated as a house, our brains have a peculiar knack of recognizing faces in everyday inanimate objects, despite the fact we know what we are looking at doesn’t actually have a face. According to a new study in the journal Psychological Science, these comical illusions arise because the neural mechanisms that encode the features of human faces are also recruited to process other images.
Known as face pareidolia, the willingness of our eyes to see faces in regular items like letterboxes or pieces of fruit can be blamed on a particular set of neurons that are primed to recognize faces and extract important social information from them – such as the emotion being portrayed by that person or whether they are looking at us.
Previous research has shown that these neurons are susceptible to sensory adaptation, whereby they modify their reading of a particular situation based on previous input. Explaining this phenomenon in a statement, study author Colin Palmer said: “if you are repeatedly shown pictures of faces that are looking towards your left, for example, your perception will actually change over time so that the faces will appear to be looking more rightwards than they really are.”
To test whether this mechanism can also be triggered by face pareidolia, researchers showed volunteers a series of pictures of inanimate objects that looked like they had faces, all of which appeared to be directing their gaze in the same direction.
When participants were then shown images of actual human faces looking directly at them, they tended to perceive these faces as gazing towards the opposite direction as the pareidolia faces. In other words, after seeing a series of images of boxes, bowling balls and handbags that all looked like they had faces that were looking to the left, people then thought that human faces staring straight ahead were peering slightly to the right.
“This is evidence of overlap in the neural mechanisms that are active when we experience face pareidolia and when we look at human faces,” explained Palmer.
The study authors say that this willingness to recognize faces probably reflects an evolutionary adaptation whereby we have become highly attuned to reading the social cues embedded within the facial expressions of other people. This is obviously a vital skill for a species that relies so heavily on social interactions in order to survive and thrive, although it can also produce some hilarious errors.