Brain size predicts learning abilities in bees

When it comes to the brain, bigger is generally considered better in terms
of cognitive performance. While this notion is supported by studies of
birds and primates showing that larger brains improve learning capacity,
similar evidence is surprisingly lacking for invertebrates. Although the
brain of invertebrates is smaller and simpler than that of vertebrates,
recent work in insects has revealed enormous variation in size across
species. Here, we ask whether bee species that have larger brains also
have higher learning abilities. We conducted an experiment in which
field-collected individuals had to associate an unconditioned stimulus
(sucrose) with a conditioned stimulus (colored strip). We found that most
species can learn to associate a color with a reward, yet some do so
better than others. These differences in learning were related to brain
size: species with larger brains — both absolute and relative to body
size— exhibited enhanced performance to learn the reward-color
association. Our finding highlights the functional significance of brain
size in insects, filling a major gap in our understanding of brain
evolution and opening new opportunities for future research.