A Comparative Perspective on Three Primate Species’ Responses to a Pictorial Emotional Stroop Task
Lester E. Fisher Center for the Study and Conservation of Apes, Lincoln Park Zoo, Chicago, IL 60614, USA
School of Psychology and Neuroscience, University of St Andrews, St Andrews KY16 9AJ, UK
Psychology, Graduate School and University Center, City University of New York, New York, NY 10016, USA
Author to whom correspondence should be addressed.
Academic Editors: Miquel Llorente and Gloria Fernández-Lázaro
Received: 25 January 2021
Revised: 17 February 2021
Accepted: 19 February 2021
Published: 24 February 2021
As animals cannot tell us how they feel, we must develop tests to make inferences about how they are feeling to assess their welfare. Here, we adapted a task that has been previously used with humans and chimpanzees to assess how chimpanzees, gorillas, and Japanese macaques respond to pictures of different emotional valences. Specifically, if the primates perceive emotionally arousing photographs differently as compared to neutral photographs, we would expect them to “trip up” more when responding to emotional stimuli. We presented the primates with a touchscreen task in which they had to select one of two differently colored squares. However, the squares always contained either positive photographs (a preferred food), negative photographs (a snake), or neutral photographs (human-made objects). The primates made more errors in selecting the correct square when the squares contained positive or negative photographs as compared to neutral photographs, indicating that they perceived these differentially, and that this caused them to make mistakes. Thus, the primates’ cognitive ability was disrupted by emotional stimuli. This offers important insights into how primates perceive the world around them, and how they process elements that may have negative or positive associations.