Three studies on configural face processing by chimpanzees.

Previous studies have demonstrated the sensitivity of chimpanzees to facial configurations. Three studies further these findings by showing this sensitivity to be specific to second-order relational properties. In humans, this type of configural processing requires prolonged experience and enables subordinate-level discriminations of many individuals. Chimpanzees showed evidence of a composite-like effect for conspecific but not human faces despite extensive experience with humans. Chimpanzee face recognition was impaired only when manipulations targeted second-order properties. Finally, face processing was impaired when individual features were blurred through pixelation. Results confirm that chimpanzee face discrimination, like humans, depends on the integrity of second-order relational properties.