Stressed bees are more likely to make pessimistic choices, according to a study published in Proceedings of the Royal Society B. The team from Newcastle University, UK, found that bumblebees don’t expect much reward when they’re agitated and stressed, which lowers their ability to pollinate flowers.
The team trained bees to pick different colors to signal something good or bad. Bees learnt to associate different colours with different outcomes, with one color associated with a good reward location and another color showing a much lower reward. Bees recognise the difference and picked the better location when shown each colour.
Once the bees learnt this distinction, the team divided them into three groups: two experienced a simulated predatory attack, and the third did not experience any stress. The bees were stressed by shaking or being trapped by a robotic arm with a sponge. The bees in the first two groups (who had experienced the attacks) were more likely to settle for low-reward locations more than the control bees.
“Our study shows that bees are more pessimistic after stress as their behavior suggests that they do not expect to get rewards,” said Dr. Vivek Nityananda from Newcastle University. “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, this research can say that bees have similar responses when stressed and make pessimistic choices. The best explanation for their behaviour is that they expect high rewards to be less likely and exhibit traits of pessimistic people.”
The team defends that this research is important because it shows how stress can impact the bee’s ability to approach flowers and pollinate plants, as well as their ability to access high-quality rewards. In addition, these results also show that many animals, including insects, show emotional.
“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. When faced with ambiguity, stressed bees, much like someone seeing the glass as ‘half empty,’ are more likely to expect negative outcomes,” said Dr Olga Procenko. “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 behaviour, which could provide insights into their responses to environmental challenges and inform conservation efforts.”
The authors recognise that further research is needed to understand the implications for pollinating flowers and plants. “We need to figure out how bees evaluate rewards when stressed and whether these states in bees show other properties we see in emotions. We also need to investigate the neural mechanisms involved and see if bees in the wild show similar responses,” concluded Dr Nityananda.
Procenko O, Read J, and Nityananda V (2024) Physically stressed bees expect less reward in an active choice judgement bias testProc. R. Soc. B.29120240512http://doi.org/10.1098/rspb.2024.0512