Humans expend a great deal of cognitive energy on recognizing both faces and the emotional content of those faces. However, according to a study by Fabian Soto and Edward Wasserman of the University of Iowa, this ability is not unique to humans. Pigeons can do it too.
Pigeons do not have a specialized system for face processing, but they still show similarities to people when they are trained to recognize human faces. (Credit: U. Iowa).
When shown an array of human faces displaying different emotions, pigeons could categorize the pictures according to either identity or emotional content. Even more intriguingly, they showed the same biases that humans show. It’s much easier for people to group all pictures of a single individual together regardless of facial expression than it is to group pictures with similar emotional expressions regardless of identity. It’s believed that this discrepancy is a direct result of our specialized human face recognition system. Why then are pigeons equally better at grouping individuals by identity than by facial expression? The authors suggest that our facial recognition abilities, far from being unique to humans, may be shared by all vertebrates.
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.