The brain is a beehive, buzzing and bustling inside with the ebb and flow of information. Whether it be through neurons or bees, both brains and beehives must make decisions; both must decide in order to survive. A new study by Prof. Tom Seeley, neurobiology and behavior, published in last month’s issue of Science, proposes a novel “bee as neuron” metaphor. It revealed that the way swarms of bees reach consensus is extraordinarily similar to the way people do.
Seeley’s prior research clarified how scout bees perform a “waggle dance” to tell hivemates where to find food and water sources and potential nest sites. Bees dancing for different sites will compete for recruits — once a critical number of bees, also called a quorum, have joined in a particular dance, then a decision is reached, Seeley said.
“But that turned out not to be the whole story — there’s another signal,” Seeley said. “And this is kind of the dark side of the decision making process.”
In addition to the positive campaigning of these excitatory “waggle dances,” competing bees will negatively campaign, inhibiting one another with “stop” signals, not unlike how neurons alternatively activate and inhibit other neurons, Seeley said.
“It’s kind of a rough signal — a bee will stop doing her ‘waggle dances’ and then she will be walking around on the swarm, and if she encounters a bee doing a ‘waggle dance’ for a different site than her own, she will go over and butt her with her head, ram against her and make this little beep sound,” Seeley said. “Each one is like a little dose of inhibition.”
These signals greatly speed up the decision making process and help avoid the kind of perilous deadlocks that might occur when the bees must choose between two equally good sites, Seeley said.
Think of the dilemma envisioned in the fable “Buridan’s ass,” wherein which a donkey, unable to decide between two bales of hay, starves. Any behavior averting such stalemates can be extremely evolutionarily advantageous.
“Why is that interesting?” Seeley said. “Because it points out that evolution has settled on a basic logic for building a decision making circuit and it does not matter whether the circuit is built out of neurons in a brain or bees in a swarm — the logic is the same.”
The research consisted of setting up two identical nest-boxes at Shoals Marine Laboratory where there are no native honeybees and no large trees to interfere as potential nesting sites.
“If we tried to do this experiment here in Ithaca, it would have failed completely because the bees would have found nest sites out in hollow trees and we would never have known where that was,” Seeley said. Shoals’ home on Appledore Island in Maine, on the other hand, offered the researchers complete control over the experiment’s parameters.
Each scout bee was labeled pink or yellow depending on which nest-box it visited and danced in favor of back at the swarm. The result: yellow bees almost exclusively butted pink dancers, and vice-versa, Seeley said.
Cross-inhibition such as this can powerfully sharpen the contrast in popularity between two sites, thereby statistically improving a swarm’s decision-making process, Seeley said. He noticed that when one site becomes even slightly more popular, the effect snowballs; yet even if a swarm discovers a poorer site initially, the swarm will still tend to converge on the best one over time he said.
In his book Honeybee Democracy, published last year, Seeley draws an analogy not only to the vertebrate brain but to higher-order phenomena as well. Originally titled Swarm Intelligence, Seeley renamed the book after considering what he deemed the spirit of the times: citing the Arab Spring, changes in Eastern Europe and the upcoming elections as influences on his decision.
“Democracy is not just a human process, it’s something that exists in the natural world,” Seeley said, noting how bee colonies are not actually monarchical despite having a so-called “Queen Bee.”
“She is not a decision-maker — not a royal decider ... in the end each bee makes its own decision whether to vote for a site or not for a site,” Seeley said.