A Zoo-housed Chimpanzee’s (Pan troglodytes) Responses to Potentially Arousing Stimuli
Abstract
In Experiment 1, we wished to determine whether a singly-housed adult male captive chimpanzee could discriminate the behavioral categories of sex and aggression. He was reinforced for selecting sexual rather than aggressive images on a touch-screen computer in a two-choice discrimination paradigm. He showed no discrimination after 24 sessions with non-human photos, but immediately selected human sexual images at above-chance levels. To explore whether this differential discrimination was due to a preference for human sexual images, he was presented with images of humans versus non-humans under non-differential reinforcement in Experiment 2. He preferred human photos if the images depicted sex, but not if the images depicted aggression. To further explore these preferences in Experiment 3 the chimpanzee was presented with images of genitalia of non-humans versus humans, genitalia versus eyes, and finally female versus male genitalia of both non-humans and humans, using non-differential reinforcement. The chimpanzee preferred human to non-human genitalia, and eyes to genitalia, but did not prefer female to male genitalia. This chimpanzee’s unusual social environment may have interfered with species-typical social preferences.