Strang Caroline, Muth Felicity
Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA.
School of Behavioural and Social Sciences, Brescia University College, London, Ontario, Canada N6G 1H2.
R Soc Open Sci. 2023 Apr 5;10(4):221322. doi: 10.1098/rsos.221322. eCollection 2023 Apr.
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.
判断偏差，即“乐观”和“悲观”，已在许多生物分类群中得到证实，然而这种行为背后的认知机制仍不清楚。在一个乐观范式中，动物被训练建立一种关联，如果有过积极体验，它们会对“模糊”刺激表现出更有利的行为。我们通过给蜜蜂一项任务来测试这种效应是否可以用刺激反应梯度的变化来解释，在这项任务中，它们的反应是在比通常测试更宽的刺激梯度上进行测试的。与之前的研究一致，我们发现有过积极体验的蜜蜂表现出判断偏差，更有可能去接触模糊刺激。然而，蜜蜂也不太可能去接触奖励刺激（S+）另一侧的刺激，因此它们的刺激反应曲线发生了偏移，峰值偏移反应减弱。在两个后续实验中，我们测试了这样一个假设，即我们的操作通过减少对照组的峰值偏移来改变蜜蜂的刺激反应曲线，从而改变了峰值偏移反应。我们发现，支持我们的假设的是，消除峰值偏移也消除了不同处理之间的差异。我们的研究结果指向了对非人类动物“乐观”行为的一种认知解释，并为考虑类似情绪的状态提供了一个新的范式。
