We started by finding examples of face pareidolia on the internet.
Now, people send us their own examples. And we also take photos of illusory faces that we see out in the world. They showed 250 of these photos to some thirty-eight hundred volunteers. And we found that people readily attribute these features to illusory faces. For example, a given illusory face might look like a fearful young boy or a grumpy older woman. There was a strong bias for people to perceive illusory faces as male rather than female. About four times as often, the researchers found. And this was the case for both female and male participants. Obviously none of these fake faces has a biological sex. Which means there is no reason for us to perceive them to have a particular gender. The fact that we do shows the illusory faces also engage our social perception system.