Vicarious reinforcement in rhesus macaques (macaca mulatta).

Area of Science:

• Neuroscience
• Primatology
• Behavioral Economics

Background:

• Observing others' outcomes profoundly influences social behavior, driving learning, cooperation, and empathy.
• Vicarious reinforcement, where individuals are affected by rewards given to others, is a proposed mechanism for these social influences.

Purpose of the Study:

• To investigate whether rhesus macaques exhibit spontaneous vicarious reinforcement.
• To determine if vicarious reinforcement influences decision-making, specifically the delivery of rewards to other individuals.
• To explore the role of attention to others in mediating vicarious reinforcement.

Main Methods:

• Utilized Pavlovian and instrumental conditioning to link visual cues with rewards to self (M1) or another monkey (M2).
• Assessed M1s' performance in instrumental trials based on cue-predicted outcomes (reward to M1, M2, or no one).
• Conducted preference tests between conditioned cues and measured attention to M2 during trials.

Main Results:

• M1s made more errors when cues predicted reward to M2 than to M1, and even more errors when no reward was predicted.
• M1s preferred cues associated with M2's reward over cues associated with no reward.
• Preference for self-reward cues over shared rewards suggested a nuanced social valuation.

Conclusions:

• Rhesus macaques demonstrate vicarious reinforcement, being influenced by observed rewards to conspecifics.
• Vicarious reward influences decisions regarding resource allocation towards or away from other individuals.
• These findings suggest vicarious reinforcement plays a key role in social learning, cooperation, and group coordination in macaques, potentially via homologous neural circuits.