Predictions about reward outcomes in rhesus monkeys

Area of Science:

• Cognitive Science
• Comparative Psychology
• Neuroscience

Background:

• Infants and animals look longer at surprising events, indicating prediction and detection of prediction failures.
• Reward prediction error (RPE) quantifies the difference between expected and actual reward outcomes.
• Existing RPE research often relies on neurobiological methods not feasible in all populations.

Purpose of the Study:

• To develop a novel behavioral task assessing monkeys' reward predictions using looking time.
• To investigate how monkeys respond to positive and negative reward prediction errors.
• To examine lifespan changes in reward prediction sensitivity in monkeys.

Main Methods:

• A novel behavioral task using looking time responses was developed for monkeys.
• Study 1: 210 semi-free-ranging monkeys were tested on positive error, negative error, and number control conditions.
• Study 2: 363 monkeys across the lifespan were assessed for responses to positive reward prediction errors.

Main Results:

• Monkeys looked longer at unexpectedly large or small rewards compared to expected rewards.
• Adolescent monkeys exhibited heightened responses to unexpected rewards.
• No significant changes in reward prediction sensitivity were observed during aging in monkeys.

Conclusions:

• Monkeys' looking responses effectively track their reward predictions.
• Monkeys share developmental patterns of reward sensitivity with humans.
• This novel approach provides insights into cognitive processes underlying reward-based decision-making.