Using a Touchscreen Paradigm to Evaluate Food Preferences and Response to Novel Photographic Stimuli of Food in Three Primate Species (Gorilla gorilla gorilla, Pan troglodytes, and Macaca fuscata)

Understanding captive animals’ preferences is important for their care and management. However, pairwise testing for preference can be time consuming, open to bias, and typically restricted to stimuli that can be presented manually. We tested the efficacy of using touchscreens to test zoo-housed primates’ food preferences and evaluated the primates’ understanding and interpretation of photographic stimuli. We showed 18 subjects (six gorillas, five chimpanzees, and seven Japanese macaques) four food stimuli (digital photographs of familiar foods presented via touchscreens) to test their preferences in a forced-choice paradigm. We presented preliminary single-food training trials before paired forced-choice test trials, which revealed subjects’ relative preferences for the four foods. To distinguish whether the primates’ responses represented conditioned associations between the stimuli and rewards, or a true understanding of the food photographs, we ran a follow-up study with novel stimuli (novel photographs of familiar foods). We combined the two novel stimuli with the four stimuli presented in the first experiment in pairwise forced-choice trials (importantly, without training trials). Subjects did not preferentially select or avoid the novel stimuli, suggesting they spontaneously interpreted the stimuli without training. While there was interindividual variation in preferences, subject choices were consistent across studies, even with the addition of novel stimuli. These results suggest that preferences for a variety of stimuli could be tested quickly, efficiently, and accurately using touchscreens.