You might not expect to find much in common between a human brain and the brain of a flying insect that’s happy to sacrifice itself, for its colony’s safety, by tearing off its entire back end in your arm. But certain bees share a personality trait with certain humans. Even if their needs are met at home, they’re compelled to go searching for new experiences. And shared brain chemistry might be what’s driving both of us.
Although the worker bees in a hive are closely related sisters, they can have different habits. Some tend to “scout,” an activity that comes in two flavors. Nest scouting happens when a swarm of bees defects from its home hive and goes in search of a new place to live; the scouts seek out good locations and then report back to the group. And food scouts go searching for new flower patches to feed from, even if the colony is already well fed. (Then they give other bees directions to the food source with a dramatic performance called a “waggle dance” that, incredibly, conveys location and distance.)
Researchers at the University of Illinois Urbana-Champaign and elsewhere did some personality testing on bees to find out how consistently scouts like to scout. Do the same bees always strike out on their own, or does everyone take shifts?
In tests on eight different colonies, the researchers found and marked the bees that worked as nest scouts or food scouts. They discovered that, while the overlap wasn't total, nest scouts were much more likely to be food scouts too. To find the bees that most liked to scout, the researchers trained a hive to eat at a feeder. Then they began placing new feeders farther away inside the bees' enclosure. The bees that were most likely to check out these alternate feeders, instead of staying at the close one, were collected and studied.
The tiny brains of the scout bees (as well as non-scouts) were cut up and examined to see which of their genes were working hardest. "Scouts and non-scouts show massive differences in brain gene activity," says senior author Gene Robinson. These differences appeared in the activity of genes controlling several brain chemicals such as glutamate and dopamine.
Was the scouts' altered brain chemistry the cause of their behavior, or a consequence of it? To find out, the team collected non-scouts and fed them sugar water laced with drugs. (Robinson says it's easy to convince honeybees to take their medicine. "Bees love sweets!")
When they ingested the brain chemical glutamate, non-scouts changed their behavior and became more likely to scout. But when they were fed with a molecule that blocks dopamine, the non-scouts were even less likely to scout than usual.
It's not clear how these neurochemicals interact to increase or decrease scouting behavior. But it seems that both glutamate and dopamine act in the bees' brains to influence their scouting personality.
Some humans, too, are more likely to go in search of new sensations. Psychologists call this behavior "novelty seeking." People who score high on this personality trait are more likely to abuse drugs. And like the bees, they display differences in how their brains handle dopamine. Novelty seeking in humans has also been linked to glutamate in the brain--again, like the bees.
It's highly unlikely that bees and humans inherited our shared brain chemistry from our distant common ancestor. (Robinson told ScienceNOW that this was "probably some kind of marine flatworm"--not an animal that would have expressed many personality traits at all.) Instead, we seem to have converged on the same behaviors, compelled by the similar actions of messenger chemicals in our brains.
Seeing our personalities reduced to the mindless actions of molecules moving through our brains can be unsettling--especially when we're being compared to insects. But it makes the lives of bees who travel far from the hive seem pretty close to home.
Liang, Z., Nguyen, T., Mattila, H., Rodriguez-Zas, S., Seeley, T., & Robinson, G. (2012). Molecular Determinants of Scouting Behavior in Honey Bees Science, 335 (6073), 1225-1228 DOI: 10.1126/science.1213962
Photo: Chiot's Run/Flickr