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Judgement bias, or ‘optimism’ and ‘pessimism’, has been demonstrated across many taxa, yet the cognitive mechanisms underlying this behaviour remain unclear. In an optimism paradigm, animals are trained to an association, and, if given a positive experience, behave more favourably towards ‘ambiguous’ stimuli. We tested whether this effect could be explained by changes to stimulus response gradients by giving bees a task where their response was tested across a wider gradient of stimuli than typically tested. In line with previous work, we found that bees given a positive experience demonstrated judgement bias, being more likely to visit ambiguous stimuli. However, bees were also less likely to visit a stimulus on the other side of the rewarded stimulus (S+), and as such had a shifted stimulus response curve, showing a diminished peak shift response. In two follow-up experiments we tested the hypothesis that our manipulation altered bees’ stimulus response curves via changes to the peak shift response by reducing peak shift in controls. We found that, in support of our hypothesis, elimination of peak shift also eliminated differences between treatments. Our results point towards a cognitive explanation of ‘optimistic’ behaviour in non-human animals and offer a new paradigm for considering emotion-like states.
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Stress produces negative judgement bias in cuttlefish
Judgement bias tasks (JBTs) are used to assess the emotional state and welfare of animals in zoos, farms and laboratories, based on the interpretation of an ambiguous or intermediate cue. Animals in positive affective states are more likely to interpret the ambiguous cue positively, whereas animals experiencing negative affect are more likely to interpret ambiguous cues pessimistically. Here, we developed a modified JBT assay for the stumpy-spined cuttlefish,Sepia bandensis, to determine whether cuttlefish exhibit negative affective states resulting from external stressors. Positive and neutral visual cues were presented twice daily until animals learned to associate food with the reinforced visual cue. After training, one treatment group was exposed to combined exposure and handling stress produced by 6 days of impoverished housing and simulated net capture. Our control group received no stress experience. In test trials performed after the stress experience, stressed animals showed higher latencies to approach ambiguous cues, spent significantly less time in rooms with ambiguous cues once they entered, and were less likely to enter first into the ambiguous cue-paired room compared with controls. These behaviours suggest that stress induces pessimistic judgement bias in cuttlefish, the first indication of this capacity in cephalopods.
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- Award ID(s):
- 2047331
- PAR ID:
- 10583118
- Publisher / Repository:
- Royal Society
- Date Published:
- Journal Name:
- Biology Letters
- Volume:
- 20
- Issue:
- 10
- ISSN:
- 1744-9561
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1098/rsbl.2024.0228
