Bumblebees Exhibit Optimism When Given Sugar

A team of researchers has found that sugar can induce a positive emotion-like state in bumblebees. The team gave bees a sugary drink and the insects showed more “optimism” in learning new tasks. The bees were also quicker to recover from a bad experience. The findings are in a paper that was just published in the journal Science.

Very little is known about insect emotions and scientists aren’t sure if invertebrates are even capable of having emotional reactions. Researchers wondered if bumblebees would change their behavior in response to being given an unexpectedly sweet drink.

The research team started training bumblebees to fly toward a cylinder target that would reward them with a sugary reward. Some of the bees were first given a sweet sucrose drink while others were just given water. The bees that were given the sucrose were quicker to learn and flew faster to the cylinder. In later trials, the researchers showed that the bees weren’t simply more exploratory after ingesting sugar. Instead, they were more optimistic about ambiguous cues such as the cylinder, showing less fear in novel situations.

The team conducted a second experiment with the bumblebees. They gave one group of bees the sucrose drink again while a control group didn’t receive any sugar. The researchers then captured and released the bees, replicating an attack by a predator. The bees that had consumed sucrose before the test were much quicker to recover. They were faster to regain composure and quickly went back to foraging behaviors.

Interestingly, the team could suppress these sugar-induced behaviors by administering a dopamine antagonist to the bees. When given the drug fluphenazine, the group receiving sucrose was indistinguishable from the control group. This shows that the positive emotion-like state was dopamine-dependent. Dopamine is a neurotransmitter that plays a role in the human brain’s reward and pleasure centers. Similar to humans, dopamine was affecting the emotional state of the bumblebees.

The findings provide evidence for the existence of emotion-like states in insects. While scientists can’t confirm whether or not bees have “feelings”, a sugary drink of sucrose caused bumblebees to exhibit optimistic behaviors.


J. Perry et al. Unexpected rewards induce dopamine-dependent positive emotion-like state changes in bumblebees. Science (2016).

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