Glass Half-Full: Optimistic Bumblebees

Charles Darwin himself expressed a belief in the presence of emotions among insects, describing expressions of anger, terror, jealousy, and love that he observed. Now, nearly 150 years later, a lot of research is being done to answer the question of whether invertebrates have emotion-like states. This is mainly driven by interest in the evolutionary roots of emotional processes and their underlying mechanisms.

In this study, researchers from the U.K. tried to determine if bumblebees show decision-making behavior similar to optimism in humans. They found that such behavior seemingly depends on dopamine, a neurotransmitter involved in the processing of reward in humans.

However, emotions are obviously highly subjective. The question is how can positive and negative feelings such as happiness and anger be assessed in non-human animals? When trying to find this out, scientists typically quantify physiological, behavioral and cognitive markers that, unlike feelings, can be measured objectively.

In the study, a sucrose solution was given to the bees to induce a positive emotional state, a state that was then confirmed via a cognitive bias test. These tests are based on previous findings that human emotions can bias decision-making under ambiguous conditions, where happy people were more likely to make optimistic judgements in ambivalent situations. To replicate this, the bumblebees were trained with a cylinder that was placed either on one side next to a green card or on the other side next to a blue card. One of the location-color combinations indicated that the cylinder had a sucrose solution reward, while the other contained simple water. The bees quickly learned to fly faster to the cylinder with the sweet liquid.

The results of the final tests were surprising – bees who received an unexpected high sucrose reward to induce a positive state before an ambiguity test, flew faster to the cylinder than non-rewarded bees. These findings suggest that such positive states can be induced in insects and that they persist for some time.

The researchers warn, however, that whether these “emotion-like” states in insects are accompanied by emotional feelings known to us, remains unanswered. However, animal advocates will surely be pleased to know that now the possibility of insect consciousness is a topic of exciting debates, discussions and innovation in the scientific community. The mere fact that insects may experience emotions may trigger compassion in fellow humans by elevating acceptance via anthropomorphism.