Stressed bees may experience human-like emotions

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Researchers from Newcastle University in Newcastle upon Tyne, England, have discovered that bumblebees’ responses to adverse events resemble human emotions. Findings of the study show that bees lower their expectations of rewards when they become agitated or stressed, which scientists say could impact their approach to pollination. The study offers significant evidence for judgement biases in bees.^1,2

“Our study shows that bees are more pessimistic after stress as their behavior suggests that they do not expect to get rewards,” Vivek Nityananda, PhD, a Biotechnology and Biological Sciences Research Council (BBSRC) David Phillips research fellow who worked on the study, said in a university release.¹ “Emotions are complex states and, in humans, involve a subjective understanding of what you are feeling. We might never know if bees feel something similar, however, what this research can say is that bees have similar responses when they are stressed and make pessimistic choices. The best explanation for their behavior is that they expect high rewards to be less likely and exhibit traits of pessimistic people.”

In the study, published in the journal Proceedings of the Royal Society B, bumblebees were required to make an active choice as part of a novel judgement bias test.² The bees were trained to associate high-tier and low-tier rewards, in 2 separate reward chambers, with distinct colors. One of the colors was associated with a sweet reward location, and the other with a much lower-tier reward. Bees learned the difference and visited the favorable location when shown both colors.^1,2

After learning these associations, 2 groups of bees were subjected to a simulated predatory attack—they were shaken and trapped by a robotic arm wielding a sponge—while a third group was left alone, not experiencing any added stress.^1,2 When presented ambiguous colors that fell somewhere between the 2 familiar colors, bees in the 2 groups that had experienced the attacks, and were under more stress, were less likely to interpret the ambiguous colors as indicators of high-tier rewards. Therefore, they visited low-tier reward locations more frequently than bees in the control group.

“Our research suggests that, like other animals, including humans, bees may experience emotion-like states when stressed, as demonstrated by a clear shift towards pessimism,” Olga Procenko, PhD, a researcher at the University of Birmingham who led the study, said in a university release.¹ “When faced with ambiguity, stressed bees, much like someone seeing the glass as ‘half empty,’ are more likely to expect negative outcomes. Besides suggesting that states akin to emotion may be evolutionarily conserved, our study opens up new possibilities for understanding how stress affects insect cognition and behavior, which could provide insights into their responses to environmental challenges and inform conservation efforts.”

The study emphasized the need for further research to fully understand the implications for the pollination of flowers and plants. It’s critical to understand if the pessimistic judgements made by the bees could be adaptive, potentially to avoid dangerous or unpredictable environments.² Further research should prioritize an understanding of how emotion-like states in bees are generated and sustained. With a deeper understanding of these mechanisms and their origin, researchers will be able to determine whether there is a common ancestry and similar states in other vertebrates, or whether they are distinct and the result of convergent evolution.²

“We need to figure out how bees evaluate rewards when stressed and whether these states in bees show other properties we see in emotions,” Nityananda said.¹ “We also need to investigate the neural mechanisms involved and see if bees in the wild show similar responses.”

References

1. Stressed bees lack a buzz in life. News release. Newcastle University. October 9, 2024. Accessed October 22, 2024. https://www.ncl.ac.uk/press/articles/latest/2024/10/pessimisticbees/?_gl=1*vhk8ku*_up*MQ..*_ga*MTAzMjE2NjEyNS4xNzI5NjA4OTQ5*_ga_VH2F6S16XP*MTcyOTYwODk0OC4xLjEuMTcyOTYwOTA1NC4wLjAuMTU0ODc0ODU0MA.
2. Procenko O, Read JCA, Nityananda V. Physically stressed bees expect less reward in an active choice judgement bias test. Proc R Soc Lond B Biol Sci. 2024;291(2032). https://doi.org/10.1098/rspb.2024.0512.