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 rather than a familiar stimulus. We then explored the boundaries of these label-based expectations by testing bees along a stimulus gradient and found that expectations generalized to similar stimuli. Such reference-dependent evaluations may play an important role in bees’ foraging choices, with the potential to impact floral evolution and plant community dynamics.