Abstract
We investigated how squirrel monkeys and humans employ various facial cues to discriminate individual faces of their own and other species. After squirrel monkeys were trained to discriminate two individual faces, they were tested with a variety of modified stimuli. The test stimuli used in experiment 1 preserved specific facial features used in training and the test stimuli in experiment 2 were faces that included facial features not used in training and those used as test stimuli in experiment 1. We compared the results to those obtained in humans (experiment 3). We found that the eyes played a significant role as cues for discrimination of individual faces. Furthermore, unlike the human subjects, monkeys used the outer facial boundary of their own species as a cue for discrimination. We suggest that squirrel monkeys may use their faces for discrimination of individuals and that the information of faces for discrimination of their own species may differ from those of other species.
