🐝 Among bees, brain size matters, but not as you think

Does a big brain make you smarter? A study published in PNAS provides a nuanced answer in bees. By testing their ability to associate odors with a reward, scientists show that individuals with more developed olfactory lobes learn better. A performance that could improve their foraging efficiency.

A tiny brain but impressive abilities

If the question of brain size and cognitive abilities is as old as the world, it still hasn't found a satisfactory answer in the scientific community. Contrary to popular belief, a larger brain is not necessarily synonymous with better cognitive performance. This rule applies equally to computers and living beings.


Insects are proof of this because despite their tiny brains (often smaller than a grain of semolina) they are capable of remarkably complex behaviors: problem solving, learning, symbolic communication, or route optimization over long distances. These abilities depend less on overall brain size than on the fine organization of its neural circuits.

Individual differences that matter

Even within a species, individuals are not identical. In the honeybee (Apis mellifera), there are natural variations in brain size.

By analyzing nearly 1,500 individuals, scientists have shown that these differences influence learning performance. The bees were conditioned to associate an odor with a sweet reward: those with the largest heads performed better, regardless of task difficulty.

These results show that some bees are naturally more efficient at learning olfactory signals, a crucial asset for locating flowers and communicating within the colony.

The key role of olfactory lobes

To understand the origin of these differences, scientists reconstructed the brain of some bees in 3D using X-rays.

The result is clear: the best learning performances are associated not with overall brain size, but with the volume of the olfactory lobes, structures located under the antennae and specialized in odor processing.

This observation was confirmed in the bumblebee (Bombus terrestris), suggesting that this link between brain structure and olfactory learning may be widespread among insects.

While this study does not provide a definitive answer on a cause-and-effect link between brain size and general intelligence in an animal, it indicates links between specific cognitive tasks (here odor learning) and well-defined areas in the brain (the olfactory lobes).

These links are potentially multiple and different depending on the cognitive operations, which could explain why individuals are good at some behaviors and less good at others. This variability is well known across the animal kingdom, from insects to humans, and contributes to characterizing animal personalities.