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The data for the first screen-peck task (no affect manipulation) are available under DOI: 10.6084/m9.figshare.2283733. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: All data are available from Figshare. Received: MaAccepted: JPublished: July 13, 2016Ĭopyright: © 2016 Deakin et al. PLoS ONE 11(7):Įditor: Dan Weary, University of British Columbia, CANADA
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Hens tested under warmer conditions were significantly more likely to peck the M probe than those tested at cooler temperatures suggesting that increased temperature in the ranges tested here may have some positive effect on hens, inducing a positive cognitive bias.Ĭitation: Deakin A, Browne WJ, Hodge JJL, Paul ES, Mendl M (2016) A Screen-Peck Task for Investigating Cognitive Bias in Laying Hens. Hens have been shown to prefer temperatures in the higher range and hence we assumed that exposure to the higher temperature would induce a relatively positive affective state. We manipulated affective state by changing temperature during testing to either ~20☌ or ~29☌ in a repeated measures cross-over design. Across six test sessions, there was no evidence for extinction of pecking responses to ambiguous cues. Cue pecking showed a clear generalisation curve from P through NP, M, NN to N suggesting that hens were able to associate colour saturation with reward or punishment, and could discriminate between stimuli that were more or less similar to learnt cues. Ambiguous cues were orange circles of intermediate saturation between the P and N cue (near-positive–NP middle–M near-negative–NN), and were unrewarded.
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In the ‘screen-peck’ task, hens were trained to peck a high/low saturation orange circle presented on a computer screen (positive cue–P) to obtain a mealworm reward, and to not peck when the oppositely saturated orange circle was presented (negative cue–N) to avoid a one second air puff. We investigated laying hens’ responses to ambiguous stimuli using a novel cognitive bias task. Investigating animals’ responses to ambiguous cues can therefore be used as a proxy measure of affective state. Animals in a more negative affective state tend to interpret ambiguous cues more negatively than animals in a more positive state and vice versa. Affect-induced cognitive judgement biases occur in both humans and animals.