Different effects of reward value and saliency during bumblebee visual search for multiple rewarding targets

Abstract

Several animals, including bees, use visual search to distinguish targets of interest and ignore distractors. While bee flower choice is well studied, we know relatively little about how they choose between multiple rewarding flowers in complex floral environments. Two factors that could influence bee visual search for multiple flowers are the saliency (colour contrast against the background) and the reward value of flowers. We here investigated how these two different factors contribute to bee visual search. We trained bees to independently recognize two rewarding flower types that, in different experiments, differed in either saliency, reward value or both. We then measured their choices and attention to these flowers in the presence of distractors in a test without reinforcement. We found that bees preferred more salient or higher rewarding flowers and ignored distractors. When the high-reward flowers were less salient than the low-reward flowers, bees were nonetheless equally likely to choose high-reward flowers, for the reward and saliency values we used. Bees were also more likely to attend to these high-reward flowers, spending higher inspection times around them and exhibiting faster search times when choosing them. When flowers differed in reward, we also found an effect of the training order with low-reward targets being more likely to be chosen if they had been encountered during the more immediate training session prior to the test. Our results parallel recent findings from humans demonstrating that reward value can attract attention even when targets are less salient and irrelevant to the current task.

Learning modifies attention during bumblebee visual search

“…After plotting the reflectance values of our flowers in this space, we were able to measure the distance in perceptual space between them. These data are provided in the previous paper (Nityananda and Chittka 2021).…”

“…While a large body of research has demonstrated reward-based learning in bees, most of the work has looked at how learning affects the choices made by bees. Much less research has investigated the influence of rewards on visual search and attention in bees (Spaethe et al 2006; Morawetz and Spaethe 2012; Nityananda and Pattrick 2013; Nityananda and Chittka 2021).…”

“…Bees have been shown to flexibly switch between multiple rewarding targets (Nityananda and Pattrick 2013; Li et al 2017). In experimental set-ups, floral rewards influence not just their choices but their visual attention, as measured by the time spent around particular flowers (Nityananda and Chittka 2021). Bees spend more time around higher rewarding flowers even when they are less salient than lower rewarding flowers.…”

“…To test these ideas, we investigated the training bouts for bees trained as part of a previously published study (Nityananda and Chittka 2021) that focussed on the behaviour of bees in tests after the training. As part of that study, bees were trained on one of two flower types – either higher reward lower saliency flowers or lower reward higher saliency flowers.…”

Decreased efficiency of pollen collection due to Sulfoxaflor exposure leads to a reduction in the size of bumble bee workers in late European summer

“…Some flowers can also present a set of floral traits (e.g., shape, color, and resources) that influence generalists' foraging behavior (Spaethe et al, 2001;Wood et al, 2021). Social bees (e.g., honey bees) are organisms performing complex tasks (Nityananda and Chittka, 2021) that together with their social communication work synergistically to mitigate the negative effects of landscape (Nürnberger et al, 2019). However, it has been shown that unhealthy or stressed bees are less efficient at performing social tasks (Boff et al, 2018;Crall et al, 2018;Raine, 2018).…”