How capuchin monkeys (Cebus apella) behaviorally cope with increasing delay in a self-control task

Area of Science:

• Primate behavior
• Animal cognition
• Ethology

Background:

• Displacement activities, like scratching, are behaviors irrelevant to a situation, facilitating state transitions.
• Scratching in primates is linked to frustration and anxiety, increasing with cognitive task difficulty in chimpanzees.

Purpose of the Study:

• To investigate displacement scratching and related behaviors in capuchin monkeys during a self-control task.
• To compare capuchin scratching behavior with that of chimpanzees in response to cognitive challenges.

Main Methods:

• Behavioral data from video clips of nine capuchin monkeys were analyzed.
• Monkeys performed a delay choice task, choosing between immediate small or delayed large rewards.
• Measures included scratching, response latency, and motor impulsivity during the delay period.

Main Results:

• Scratching, response latency, and motor impulsivity decreased across sessions as capuchins habituated to the task.
• A bias for choosing options on one side of the apparatus increased over time.
• Unlike chimpanzees, no handedness in scratching behavior was observed in capuchins.

Conclusions:

• Capuchins may perceive the delay choice task as less stressful over time due to faster, more automatic responses.
• Habituation to task contingencies could also explain the observed behavioral changes.
• Further research is needed to confirm the absence of scratching handedness in capuchins.