Label-based expectations affect reward perception in bumblebees

While classic models of animal decision-making assume that individuals objectively assess the absolute value of options, decades of research have shown that rewards are often evaluated relative to prior experience, creating ‘contrast effects’. Contrast effects are often assumed to be purely sensory, yet consumer psychology tells us that label-based expectations can affect value perception. However, this has rarely been tested in non-model systems. Bumblebees forage on a variety of flower types that vary in their signals and rewards and show clear contrast effects when rewards are lower than their immediate previous experience. Here we manipulated bees’ expectations of a stimulus’ quality, before downshifting the reward to induce incentive contrast. We found that contrast effects were not solely driven by prior experience with a better reward, but also influenced by experience with associated stimuli. Bees were faster to accept the lower-quality reward when it was paired with a novel rat...尽管经典的动物决策模型假定个体能够客观评估选项的绝对价值，但数十年的研究表明，动物通常会基于既往经历对奖励进行相对评估，由此产生对比效应（contrast effects）。过往研究往往认为对比效应仅由感官通路介导，但消费心理学领域的研究显示，基于标签的预期会影响个体的价值感知。然而，这类效应极少在非模式生物系统（non-model systems）中得到验证。熊蜂（bumblebees）会取食多种信号特征与奖励组分均存在差异的花卉类群，且当当前奖励低于其近期既往经历时，会表现出清晰的对比效应。本研究中，我们先调控熊蜂对刺激物（stimulus）质量的预期，随后通过下调奖励水平以诱导动机对比效应（incentive contrast）。研究结果表明，对比效应并非仅由既往获得更优奖励的经历所驱动，同时还会受到关联刺激物相关经历的影响。当低质量奖励与一种新型大鼠相关联时，熊蜂会更快地接受该奖励……