Chimpanzees return favors at a personal cost

Area of Science:

• Primatology
• Evolutionary Psychology
• Behavioral Ecology

Background:

• Human cooperation involves personal cost, but chimpanzee motivations remain unclear.
• Limited understanding of the evolutionary basis of prosocial behavior in non-human primates.

Purpose of the Study:

• To experimentally investigate the motivational underpinnings of prosocial resource allocation in chimpanzees (Pan troglodytes).
• To determine if chimpanzees reciprocate assistance and are sensitive to the risks partners undertake.

Main Methods:

• Chimpanzees chose between options delivering food to self/partner or only self.
• Partner's prior assistance (or lack thereof) and risk-taking were manipulated.
• Behavioral choices were recorded to assess prosocial tendencies.

Main Results:

• Chimpanzees significantly increased prosocial choices after receiving partner assistance.
• This effect persisted even when prosocial choices incurred material costs for the subject.
• Subjects showed increased prosociality when partners risked food to provide assistance.

Conclusions:

• Chimpanzees demonstrate reciprocal altruism, incurring costs to benefit partners who previously assisted them.
• Sensitivity to partner's risk suggests sophisticated understanding in decision-making.
• Findings indicate potential deep phylogenetic roots for key human cooperative motivations.