International Journal of Comparative Psychology

In this experiment, orangutans’ ability to use social versus non -social cues on an object-choice task was examined. In addition, the role of spatial proximity was investigated, by matching the distance between the cue and the target object across both social and non-social conditions. Subjects took significantly fewer trials to learn to use social cues (a finger touching the target object and an experimenter’s face hovering above the target object) than non -social cues (paper markers). There was no statistical difference between their performance with cues that were physically contiguous with the target object and those that were distal spatially, regardless of whether the cue was social ornon-social in nature. Evidence for spontaneous cue use was strongest for the social-contiguous condition (a finger touching the target object). These results suggest that spatial proximity alone cannot explain apes’ performance on these types of tasks. Although subjects may have difficulty deriving information from human-based gestures, they still appear to be more attuned to these cues than to abstract physical markers that are matched in terms of spatial relationship and reliability.