February 2021
Vol 7, Issue 9

About The Cover

Cover image expansion

ONLINE COVER Prosocial behavior, in which individuals voluntarily perform actions intended to benefit others, is considered central to human social abilities and has been previously investigated in chimpanzees through numerous studies. However, many of these experiments have taken place indoors and with chimpanzee pairs selected by humans rather than by the apes themselves. To study chimpanzee prosocial behavior under more natural circumstances, van Leeuwen et al. observed three chimpanzee groups (consisting of 11, 25, and 44 members) in an outdoor Zambian sanctuary equipped with a button that activated a juice fountain in the enclosure beyond the pusher's reach. They observed that chimpanzees in all groups pushed the button more frequently and for longer durations as the experiment progressed, indicating that the chimpanzees were willing to act purely for the benefit of other group members. However, the researchers also observed that more members benefited per button push in some groups than in others. Since the fewest members benefited per button push in the medium-sized group, the authors conclude that these differences were not merely tied to group size, noting that each group's prosocial patterns corresponded with the group's social tolerance level. [CREDIT: CLARA DUBOIS AT CHIMFUNSHI WILDLIFE ORPHANAGE TRUST, ZAMBIA]