Bees reveal emotion-like reactions, from 'lip licking' to head shaking

New research proving bumblebees exhibit emotion-like behaviors—previously thought to exist only in mammalian species—has implications for how scientists understand the consciousness of insects.  

The first-of-its-kind study, published in Proceedings of the National Academy of Sciences, used slow-motion video to capture how bumblebees shake their heads and wipe their mouths if they don't like food—and "lick their lips" if they do.

Professor Andrew Barron from Macquarie University in Sydney, Australia, says the revelation changes our scientific understanding of the inner life of insects.

"Facial expressions are an important window into the internal states of animals. There's always been a tension between thinking of insects as animals or some sort of mini-robots. This is another step toward showing there's an inner life to being a bee."

Led by researchers Fei Peng and Cwyn Solvi at Southern Medical University in Guangzhou, China, the study of 18 colonies of bumblebees (Bombus terrestris) found the insects could show observable "liking and disliking" behaviors, as opposed to "wanting" actions or feeding reflexes.

"Many people are comfortable saying that insects can sense, learn and make decisions, but much less comfortable saying that they may evaluate things as pleasant or unpleasant. Our findings push on that intuition.

Key findings include:

• The bumblebees displayed distinctly different orofacial behaviors after consuming sweet liquids versus bitter and salty liquids.

• Post-consumption glossa ("tongue") protrusions—akin to "licking their lips"—occurred after eating sugar solutions.

• Aversive head shaking and mouth wiping occurred after tasting salty and bitter liquids.

• This emotion-like behavior has never been observed outside mammals.

A practical read on bee inner life

"We don't yet understand what the bees truly experience, but we can observe emotion-like behaviors," says Barron, a neuroethologist who studies the connections between animal behavior and its underlying control by the nervous system.

"What's important is we've now got a practical read on their inner life that we can work with experimentally."

Barron says the implications extend beyond bees to all insects.

Tiny brains, bigger ethical questions

"In terms of how the brain is organized, there's no major difference between a bee and a fly—this means there's more to consider in terms of how we might treat or react to insects. By human standards, the bee brain is tiny—weighing less than a milligram—and yet our evidence suggests the remarkable bee brain can support a form of bee inner life."

He says the work is an important step toward understanding how brain activity relates to subjective experience.

"We hope further studies will show how the bee's mental life arises from mechanisms in the brain so we can close the gap between the mental and the physical."