Bumblebees exhibit observable reactions to tastes, extending their tongues for sweet substances and shaking their heads at bitter ones, according to a new study. These behaviors, observed for the first time in insects in response to pleasant or unpleasant tastes, suggest that bees may possess a more complex inner life than previously understood, potentially mirroring aspects of mammalian emotional responses.
Researchers fed bumblebees solutions containing sugar, salt, or quinine. After tasting sweet solutions, the bees repeatedly extended their glossa, a tongue-like structure. The sweeter the solution, the more frequently this behavior occurred. Conversely, when presented with salt or quinine, the bees shook their heads and appeared to wipe their mouths, actions interpreted as signs of disgust.
Intriguingly, bees also extended their tongues when drinking fresh or saltwater if they had been deprived of fluids, hinting that the behavior might indicate enjoyment rather than simply a reaction to sugar. The study, published in the journal PNAS, utilized pharmacological techniques to explore the underlying mechanisms.
Scientists found that the tongue-sticking behavior was not linked to dopamine-driven feeding motivation systems. Instead, it appeared to be influenced by a neural endocannabinoid pathway, which in mammals is associated with emotional evaluation. This suggests that the bee's response may be related to affective, or emotional, assessment.
While bee brains are small, weighing less than a milligram, previous research has demonstrated their capacity for complex behaviors, including solving puzzles, using tools, recognizing faces, and understanding the concept of zero. These abilities have often been explained through mechanical or computational terms. However, the newly observed taste-related facial expressions could provide a basis for a more complex understanding of bee psychology.
Professor Andrew Barron of Macquarie University, a co-author of the study, stated that while the exact subjective experience of bees remains unknown, their emotion-like behaviors can be observed and studied experimentally. He noted that this research challenges the view of insects as mere robots and supports the idea of an inner life.
The researchers suggest that the bee brain may support a more complex inner life than previously assumed, moving beyond simple sensory input and decision-making to include pleasantness or unpleasantness evaluation. Future research aims to connect brain activity with subjective experience to understand how inner life emerges from neural processes.
Barron added that the similar neural organization between bees and flies means these findings could have implications for how humans interact with and perceive insects more broadly. The study indicates that the capacity for such reactions may not be unique to bees within the insect world.