Pareidolia Faces More Likely to be Perceived as Male than Female, New Study Reveals

Despite our fluency in reading human faces, sometimes we mistakenly perceive illusory faces in objects, a phenomenon known as face pareidolia. In a new series of experiments, researchers in the Laboratory of Brain & Cognition at the National Institute of Mental Health and the School of Psychology at the University of Queensland have found that illusory faces in inanimate objects are readily perceived to have a specific emotional expression, age, and gender; most strikingly, the authors have observed a strong bias to perceive illusory faces as male rather than female, at a ratio of 4:1.

Face pareidolia is the spontaneous perception of illusory facial features in inanimate objects, and can be thought of as a natural error of our face detection system.

It has recently been shown that non-human primates also experience face pareidolia, and that illusory faces engage similar neural mechanisms to real faces in the human brain.

However, it is unclear to what degree higher-level social perception beyond the detection of a face occurs in pareidolia.

Investigation of face evaluation in illusory faces has the potential to reveal new insight into the underlying mechanisms of face perception.

A key feature of face pareidolia is that it involves the spontaneous perception of a face in an inanimate object, and consequently it is an example of face perception that is divorced from many characteristics that typically accompany the faces of living organisms, such as the motion of facial muscles (e.g., to form emotional expressions), chronological age, and biological sex.

“Face pareidolia, the illusion of seeing a facial structure in an everyday object, tells us a lot about how our brains detect and recognise social cues,” said Dr. Jessica Taubert, a researcher in the School of Psychology at the University of Queensland.

“The aim of our study was to understand whether examples of face pareidolia carry the kinds of social signals that faces normally transmit, such as expression and biological sex.”

“Our results showed a striking bias in gender perception, with many more illusory faces perceived as male than female.”

“As illusory faces do not have a biological sex, this bias is significant in revealing an asymmetry in our face evaluation system when given minimal information.”

“The results demonstrate visual features required for face detection are not generally sufficient for the perception of female faces.”

A total of 3,815 adults (mean age – 39.6 years) participated in the experiments via the online crowdsourcing platform Amazon Mechanical Turk.

The participants were shown numerous examples of face pareidolia and inanimate objects with no facial structure and they were asked to indicate whether each example had a distinct emotional expression, age, and biological sex, or not.

“We know when we see faces in objects, this illusion is processed by parts of the human brain that are dedicated to processing real faces, so in theory, face pareidolia ‘fools the brain’,” Dr. Taubert said.

“The participants could recognise the emotional expressions conveyed by these peculiar objects and attribute a specific age and gender to them.”

“Now we have evidence these illusory stimuli are being processed by the brain by areas involved in social perception and cognition, so we can use face pareidolia to identify those specific areas.”

“We can compare how our brains recognise emotion, age, and biological sex, to the performance of computers trained to recognize these cues.”

“Further we can use these interesting stimuli to test for abnormal patterns of behavior.”

The results appear in the Proceedings of the National Academy of Sciences.

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Susan G. Wardle et al. 2022. Illusory faces are more likely to be perceived as male than female. PNAS 119 (5): e2117413119; doi: 10.1073/pnas.2117413119