Cognitive bias in rhesus macaques (Macaca mulatta), a novel measure of animal welfare

  • E.J. Bethell

Student thesis: Doctoral Thesis


This thesis presents the development and application of methods to assess
cognitive markers of emotion and psychological wellbeing in a species of nonhuman primate, the rhesus macaque (Macaca mulatta). In humans, vulnerability to emotional disorders such as anxiety and depression is characterized by particular cognitive profiles, known as cognitive biases. For example, anxious people automatically attend to threat-relevant information, interpret ambiguous information negatively, and have negative expectations of future events. In this thesis, I first describe two treatments that were used prior to cognitive testing to induce positive and negative shifts in inferred affective state in the monkeys (enrichment and a health-check, respectively) and discuss the impact of these treatments on the monkeys’ behaviour and physiology (Chapters 2 and 3). In the first cognitive study (Chapter 4), I present a method that uses eye-gaze to assess the extent to which threatening (versus non-threatening) stimuli capture visual spatial attention when two stimuli are presented at different locations. In the second study (Chapter 5), I present a simple operant touch-screen task to assess the extent to which a threatening distractor stimulus captures attention and impairs performance on an ongoing task when presented at the same location as the taskrelevant stimulus. In the third study (Chapter 6), I present a Go/NoGo touchscreen task to assess judgements about the reward value of ambiguous stimuli. In all of these studies, the two treatments led to different cognitive profiles in the monkeys. Monkeys showed a) automatic capture of attention by threatening stimuli, which was followed by avoidance following the health-check, but not Post-enrichment; b) impaired task performance when a threatening distractor stimulus was presented Post-health-check, and improved performance on these trials Post-enrichment; and c) a more negative judgement about the reward value of ambiguous stimuli Post-health-check versus Post-enrichment. I discuss these cognitive biases in light of available data from humans, and recent work with nonhuman animals. These data indicate that furthering our understanding of primate and other animal psychological wellbeing, may be achieved through the development of measures of cognitive bias, such as those presented here.
Date of Award2009
Original languageEnglish

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