Face it: Human perception isn’t unique

U. IOWA (US) — Humans aren’t the only ones who are able to recognize facial identity and emotional expression—pigeons can too.

The findings could make scientists reconsider assumptions about how unique human cognitive processes really are when they interact with more complex tasks such as face recognition.

In a new study, pigeons were shown photographs of human faces that varied in the identity of the face, and in emotional expression, such as a frown or a smile. In one experiment, pigeons were able to perceive the similarity among faces sharing identity and emotion.

In a second, pigeons had to categorize photographs using only one quality and ignoring the other. It was easier to ignore emotion and recognize face identity than the other way around.

The research is reported in the Journal of Vision.

“The point of the project is not that pigeons perceive faces just as we do or that people do not have specialized processes for face perception,” says Ed Wasserman, professor of experimental psychology at the University of Iowa.

“Rather, the point is that both specialized and general processes are likely to be involved in peoples’ recognition of faces and that the contributions of each should be carefully determined empirically.”

Pigeons were used for the study because they have excellent vision and are not close evolutionary relatives of humans. While they don’t have a specialized system for face processing, they still show similarities to people when they are trained to recognize human faces.

The simplest interpretation of these similarities is that they result from general recognition processes shared by both species.

“This asymmetry has been found many times in experiments with people and it has always been interpreted as the result of the unique organization of the human face processing system,” says graduate student Fabian Soto. “We have provided the first evidence suggesting that this effect can arise from perceptual processes present in other vertebrates.

“It is a popular practice among researchers in perception and cognition to speculate about specialized mechanisms without offering convincing empirical data to support their ideas,” says Wasserman.

“We hope that our research will prompt other researchers to conduct more comparative work to assess their claims about the evolution of uniquely human perceptual and cognitive processes.”

The research was funded by grants from the National Institute of Mental Health and the National Eye Institute.

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