Memory for Pictures of Upright and Inverted Primate Faces in Humans (Homo sapiens), Squirrel Monkeys (Saimiri sciureus), and Pigeons (Columba livia )

Humans ( Homo sapiens ) and squirrel monkeys ( Saimiri sciureus ) were tested for memory of upright and inverted primate faces. Working memory was tested in Experiment 1 with a delayed matching-to-sample procedure, and reference memory was examined in Experiment 2 by requiring subjects to learn to discriminate between successive pairs of upright or inverted pictures. Both human and monkey subjects showed better working memory for upright than for inverted human faces and better reference memory for upright than for inverted human and great ape faces. In Experiment 3, reference memory tests with pigeons ( Columba livia ) showed no effects of inversion on rate of learning with face pictures. We argue that these findings cannot be explained easily by an individual primate's lifetime experiences with primate faces. We suggest that similar evolved mechanisms for primate face recognition in people and monkeys are responsible for the pattern of data reported.