Capuchin monkeys (Sapajus [Cebus] apella) prefer larger sooner sequence payouts

Area of Science:

• Cognitive psychology
• Primate behavior
• Evolutionary decision-making

Background:

• The peak-end effect influences human experience evaluations based on intense or final moments.
• This bias is inconsistently observed in nonhuman primates, with prior monkey studies yielding contradictory results.
• Understanding species-specific decision-making biases is crucial for evolutionary insights.

Purpose of the Study:

• To investigate whether capuchin monkeys (Sapajus [Cebus] apella) exhibit peak-end effect biases.
• To clarify the role of experimental procedures in observed primate decision-making inconsistencies.
• To explore the evolutionary origins of decision-making biases.

Main Methods:

• A manual two-item food sequence task was administered to 14 capuchin monkeys.
• Monkeys' choices between food items of differing values were recorded.
• The impact of replacing a low-value item with a delay on choice behavior was assessed.

Main Results:

• Capuchin monkeys consistently demonstrated a "start bias," preferring to consume the higher-value item first.
• This start bias was more pronounced in low- and middle-ranking individuals.
• Choice behavior was not significantly affected when a low-value item was replaced by a delay, suggesting it was discounted.

Conclusions:

• Capuchin monkeys display a start bias, not the end bias typical of human decision-making.
• Methodological factors may influence observed biases in primate decision-making studies.
• The findings contribute to understanding the evolution of decision-making biases across species.