A Comparative Perspective on Three Primate Species' Responses to a Pictorial Emotional Stroop Task

Area of Science:

• Cognitive Psychology
• Primate Behavior
• Comparative Cognition

Background:

• The Stroop effect demonstrates cognitive interference from competing demands.
• Emotional stimuli can induce Stroop-like effects by capturing attention.
• Previous research has not extensively explored emotional Stroop effects in non-human primates.

Purpose of the Study:

• To adapt and apply pictorial Stroop test methods to assess cognitive interference in primates.
• To investigate whether primates exhibit an emotional Stroop effect.
• To compare the performance of chimpanzees, gorillas, and Japanese macaques on Stroop tasks.

Main Methods:

• Adapted pictorial Stroop test methods for touchscreen use with 19 primates (chimpanzees, gorillas, Japanese macaques).
• Subjects underwent pre-test training, with 10 reaching criterion for further testing.
• Tested subjects on a standard color-interference Stroop test and an emotional Stroop task using food and snake images.

Main Results:

• Primates demonstrated differential accuracy on the standard color-interference Stroop test.
• In the emotional Stroop task, primates were less accurate with emotionally laden stimuli compared to control stimuli.
• Accuracy rates were reduced by test stimuli in both Stroop tasks, but response latencies did not differ across trial types.

Conclusions:

• Primates exhibit cognitive interference effects analogous to the human Stroop effect, particularly with emotional stimuli.
• Differences in response patterns were observed between apes and monkeys in the emotional Stroop task.
• Contrary to some prior research, no significant differences in response latencies were found across trial types in this study.