Tonkean macaques do not prefer the helper or the hinderer in the hill paradigm

Abstract

Evaluating others prosocial tendencies can benefit individuals by allowing them to interact with prosocial individuals and avoid antisocial ones. The ontogeny of humans strong prosocial preference has been widely investigated using the hill paradigm. Childrens preference for helper over hinderer agents was measured after they watched a scene in which the helper agent pushed a climber up a hill while the hinderer agent pushed the climber down the hill. Bonobos tested with the hill paradigm preferred the hinderer over the helper, contrasting previous findings for other nonhuman primates. We tested Tonkean macaques (Macaca tonkeana) using the same procedure as the one used with bonobos to see whether they would also exhibit a hinderer preference. Subjects did not prefer the helper over the hinderer (or vice versa). The low attentional level observed in our subjects suggests a lack of interest in the video stimuli. This finding relates to more general questions regarding how animals perceive abstract animated onscreen stimuli and the relevance of the hill paradigm in investigating prosocial preferences. Studies using various experimental paradigms with conspecifics or human actors as social agents are needed to investigate further the social evaluation of prosocial behaviours in Tonkean macaques, bonobos, and other primates.