Professor David Alais, lead author of the study from the University of Sydney’s school of psychology, said: “From an evolutionary perspective, it seems that the benefit of never missing a face far outweighs the errors where inanimate objects are seen as faces.
“There is a great benefit in detecting faces quickly, but the system plays ‘fast and loose’ by applying a crude template of two eyes over a nose and mouth.
“Lots of things can satisfy that template and thus trigger a face detection response.”
Researchers say this facial recognition happens lightning-fast in the brain – within a few hundred milliseconds.
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Prof Alais said: “We know these objects are not truly faces, yet the perception of a face lingers. We end up with something strange – a parallel experience that it is both a compelling face and an object. Two things at once.”
This error is known as face pareidolia and is such a common occurrence that people accept the notion of detecting faces in objects as normal.
As well as imagining faces, humans give them emotional attributes.
Experts say this happens because, as deeply social beings, simply detecting a face is not enough.
According to the study, published in the Proceedings of the Royal Society B, once a false face is recognised by the brain it is analysed for its facial expression in the same way as a real face.
“We need to read the identity of the face and discern its expression. Are they a friend or a foe? Are they happy, sad, angry, pained?” explained Prof Alais.