Stressed bees are more likely to make pessimistic choices – indicating that their response to setbacks resembles human emotions, scientists have found.
Researchers at Newcastle University trained bumblebees to decide whether a color signaled something good or bad.
The bees learned that one color led to a sweet reward location and another had a less sucrose-soaked outcome.
Once bees learned these associations, two groups experienced a simulated attack, and a third group did not experience any external stress.
When shown an ambiguous color, the bees that came under simulated attack were less likely to interpret the color as indicating a high reward and instead visited low reward locations more than the "control" bees that had not been stressed.
Vivek Nityananda, a behavioral scientist from Newcastle University, said: "Our study shows that bees are more pessimistic after stress as their behavior suggests that they do not expect rewards.
"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."
Olga Procenko, who led the study, said: "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."
The research is published in the aptly-named biological research journal Proceedings of the Royal Society B.
