Development of social interaction preference in chimpanzees

A recent study by Lewis et al. (2025) found that chimpanzees and children prefer to watch videos featuring social interactions over non-social controls, even when this preference implied a cost on the participant (giving up rewards). These results suggest that curiosity about social content is deeply rooted in the great ape lineage. The researchers also observed developmental differences—particularly between sexes—among the children: boys showed an increasing preference for negative interactions, while girls exhibited a growing interest in positive social interactions between the ages of four and six. Since only adult chimpanzees were tested, the study could not assess developmental trajectories in non-human apes. Additionally, the videos used contrasted interactions between two individuals with videos of a single individual acting alone. As a result, the social content between the two conditions was not matched, which may have influenced looking time differences. To address this limitation, we will present videos in which the same two individuals are either interacting socially (social condition) or acting alone (control), ensuring that the overall number of individuals remains constant. Each video will depict the same number of individuals performing the same actions; the only difference will be the presence or absence of implied social interaction. In a forced-choice task, participants will have to decide for one of the videos, which results in the other video becoming unavailable. The aims of this study are twofold: first, to determine whether chimpanzees prefer social interactions over individual actions in matched controls and second, to examine whether this preference changes over the course of ontogenetic development in chimpanzees. With this study we seek to investigate whether chimpanzees are inherently more interested in watching social interactions —not simply due to the number of individuals shown, but instead because of the important social information that social interactions may convey. In doing so, we aim to determine whether social attention abilities are shared with a common ancestor of humans and other great apes.