Judging Gorilla Affect from Judgement Bias Tests

For this Hot Topics in Welfare feature, we are highlighting the research of Dr. Jennifer Vonk, who is currently a Professor of Psychology at Oakland University. The broad goal of her research with the gorillas at the Detroit Zoo is to examine their emotional well-being by assessing their affect (i.e., optimism or pessimism) in response to different environmental conditions (e.g., season, habitat access, browse availability). Judgement bias tests – a type of cognitive bias test – were used to evaluate whether gorillas judged ambiguous stimuli as being likely to lead to reward (optimism) or not lead to reward (pessimism). However, because the gorillas found the discriminations difficult to learn, they were subsequently presented with a response slowing task developed by Bethell and colleagues (2016; 2019) in which they responded to threatening and non-threatening images of either unfamiliar (McGuire & Vonk, 2020) or familiar gorillas (in preparation). The findings of these studies point to the importance of assessing the impact of manipulations at the individual level. Despite some challenges, these types of cognitive bias tasks show promise for revealing underlying affective states in nonverbal animals. To learn more about the use of cognitive bias paradigms in assessing primate welfare, watch a video presentation (https://youtu.be/fjU1_0uUBx4) about this research narrated by Dr. Vonk. 


Bethell, E. J., Cassidy, L. C., Brockhausen, R. R., & Pfefferle, D. (2019). Toward a standardized test of fearful temperament in primates: A sensitive alternative to the human intruder task for laboratory-housed Rhesus Macaques (Macaca mulatta). Frontiers in psychology10, 1051.

Bethell, E. J., Holmes, A., MacLarnon, A., & Semple, S. (2016). Emotion evaluation and response slowing in a non-human primate: New directions for cognitive bias measures of animal emotion? Behavioral Sciences6(1), 2.

McGuire, M. C. & Vonk, J. (2018). Gorillas (Gorilla gorilla gorilla) fail to learn abstract cues of differential outcomes in a novel cognitive bias test. Animal Behavior and Cognition, 5, 103-117.

McGuire, M.C., & Vonk, J. (2020). In or out: Response slowing across housing conditions as a measure of affect in three western lowland gorillas (Gorilla gorilla gorilla). PeerJ, 8, e9525.

McGuire, M., Vonk, J., Fuller, G., & Allard, S. (2017a). Using an ambiguous cue paradigm to assess cognitive bias in gorillas (Gorilla gorilla gorilla) during a browse manipulation. Animal Behavior and Cognition, 4, 91-104.

McGuire, M.C., Vonk, J. & Johnson-Ulrich, Z. (2017b). Ambiguous results when using the ambiguous-cue paradigm to assess learning and cognitive bias in gorillas and a black bear. Behavioral Sciences, 7(3), 51.

Dr. Vonk works with the bachelor troop at the Detroit Zoo. From left to right are silverback gorillas Chipua (Chip), Pendeke (Pende), Kongo. Photo credit: Roy Lewis.
Pende and Kongo in their habitat at the Detroit Zoo. Photo credit: Roy Lewis.
Kongo participating in the task.