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Article

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

1
Lester E. Fisher Center for the Study and Conservation of Apes, Lincoln Park Zoo, Chicago, IL 60614, USA
2
School of Psychology and Neuroscience, University of St Andrews, St Andrews KY16 9AJ, UK
3
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
Animals 2021, 11(3), 588; https://doi.org/10.3390/ani11030588
Received: 25 January 2021 / Revised: 17 February 2021 / Accepted: 19 February 2021 / Published: 24 February 2021
(This article belongs to the Special Issue Non-human Primates: Emotion, Cognition and Welfare)
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.
The Stroop effect describes interference in cognitive processing due to competing cognitive demands. Presenting emotionally laden stimuli creates similar Stroop-like effects that result from participants’ attention being drawn to distractor stimuli. Here, we adapted the methods of a pictorial Stroop study for use with chimpanzees (N = 6), gorillas (N = 7), and Japanese macaques (N = 6). We tested all subjects via touchscreens following the same protocol. Ten of the 19 subjects passed pre-test training. Subjects who reached criterion were then tested on a standard color-interference Stroop test, which revealed differential accuracy in the primates’ responses across conditions. Next, to test for an emotional Stroop effect, we presented subjects with photographs that were either positively valenced (a preferred food) or negatively valenced (snakes). In the emotional Stroop task, as predicted, the primates were less accurate in trials which presented emotionally laden stimuli as compared to control trials, but there were differences in the apes’ and monkeys’ response patterns. Furthermore, for both Stroop tests, while we found that subjects’ accuracy rates were reduced by test stimuli, in contrast to previous research, we found no difference across trial types in the subjects’ response latencies across conditions. View Full-Text
Keywords: affect; attentional bias; cognitive bias; emotions; snake detection theory; stroop effect; touchscreen; welfare; zoo affect; attentional bias; cognitive bias; emotions; snake detection theory; stroop effect; touchscreen; welfare; zoo
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MDPI and ACS Style

Hopper, L.M.; Allritz, M.; Egelkamp, C.L.; Huskisson, S.M.; Jacobson, S.L.; Leinwand, J.G.; Ross, S.R. A Comparative Perspective on Three Primate Species’ Responses to a Pictorial Emotional Stroop Task. Animals 2021, 11, 588. https://doi.org/10.3390/ani11030588

AMA Style

Hopper LM, Allritz M, Egelkamp CL, Huskisson SM, Jacobson SL, Leinwand JG, Ross SR. A Comparative Perspective on Three Primate Species’ Responses to a Pictorial Emotional Stroop Task. Animals. 2021; 11(3):588. https://doi.org/10.3390/ani11030588

Chicago/Turabian Style

Hopper, Lydia M., Matthias Allritz, Crystal L. Egelkamp, Sarah M. Huskisson, Sarah L. Jacobson, Jesse G. Leinwand, and Stephen R. Ross 2021. "A Comparative Perspective on Three Primate Species’ Responses to a Pictorial Emotional Stroop Task" Animals 11, no. 3: 588. https://doi.org/10.3390/ani11030588

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