Abstract
Negative affect in humans and animals is known to cause individuals to interpret ambiguous stimuli pessimistically, a phenomenon termed 'cognitive bias'. Here, we used captive European starlings (Sturnus vulgaris) to test the hypothesis that a reduction in environmental conditions, from enriched to non-enriched cages, would engender negative affect, and hence 'pessimistic' biases. We also explored whether individual differences in stereotypic behaviour (repetitive somersaulting) predicted 'pessimism'. Eight birds were trained on a novel conditional discrimination task with differential rewards, in which background shade (light or dark) determined which of two covered dishes contained a food reward. The reward was small when the background was light, but large when the background was dark. We then presented background shades intermediate between those trained to assess the birds' bias to choose the dish associated with the smaller food reward (a 'pessimistic' judgement) when the discriminative stimulus was ambiguous. Contrary to predictions, changes in the level of cage enrichment had no effect on 'pessimism'. However, changes in the latency to choose and probability of expressing a choice suggested that birds learnt rapidly that trials with ambiguous stimuli were unreinforced. Individual differences in performance of stereotypies did predict 'pessimism'. Specifically, birds that somersaulted were more likely to choose the dish associated with the smaller food reward in the presence of the most ambiguous discriminative stimulus. We propose that somersaulting is part of a wider suite of behavioural traits indicative of a stress response to captive conditions that is symptomatic of a negative affective state.
DOI
10.1007/s10071-010-0323-z
Publication Date
2010-09-01
Publication Title
Animal Cognition
Volume
13
Issue
5
Publisher
Springer Science and Business Media LLC
ISSN
1435-9456
Embargo Period
2024-11-22
First Page
721
Last Page
731
Recommended Citation
Brilot, B., Asher, L., & Bateson, M. (2010) 'Stereotyping starlings are more ‘pessimistic’', Animal Cognition, 13(5), pp. 721-731. Springer Science and Business Media LLC: Available at: https://doi.org/10.1007/s10071-010-0323-z
