Egelkamp, C. L., Leahy, M. A., Ross, S. R. et al. 2018. Testing food preferences in zoo-housed apes with touchscreens. American Journal of Primatology 80(S1), 30 (40th Meeting of the American Society of Primatologists Scientific Program, Abstract #58).
Preference testing has many benefits, informing both applied management decisions and theoretical questions. We developed a preference‐testing method in which subjects are shown pairs of photographs of food items on a touchscreen in a forced‐choice paradigm and rewarded with the food they select. In this paradigm, the relative frequency of selections represents the subject's relative food preferences. We evaluated this method with a zoo‐housed male gorilla (Gorilla gorilla gorilla). His relative‐preferences for four foods (grape, carrot, turnip, and cucumber) were tested in six pairwise tests, with 90 trials per pairing. In pairings in which each of the foods was offered, the subject selected grape in 96% of trials, carrot in 53%, cucumber in 30%, and turnip in 21%. Food pairing had a significant effect on the subject's selection rate for carrot (p < .001) and cucumber (p < .001), but only for turnip in certain pairings, and not for grape in any pairing. The subject displayed a significant preference for grape, selecting it above chance across food pairings (p < 0.001), while his selection for other foods varied by pairing, revealing his relative preferences for those food items. These results correspond with the subject's preferences measured previously with a manual preference test and validate that touchscreens can be used to assess primate food preferences. This new methodology is now being implemented with additional gorillas and also chimpanzees (Pan troglodytes).