Differentiated responses to different human conditions by chimpanzees.

Chimpanzees' responses to human conditions were investigated. In the experimental condition, the experimenter pretended to injure the index finger, and in the control condition, the experimenter smiled and waved her hand to the chimpanzees. Although looking behavior was observed in both conditions, there was a difference in these types of behavior. Subjects seemed to concentrate their gaze on the experimenter's behavior in the experimental condition. The finding suggests the possibility that such different behaviors may be a basis for empathic behavior similar to that of human infants.