Honeybees Can Avoid Deadlock When Making Group Decisions, So Why Can't We?

**Note: This article was adapted in part from previous posts written on group decision-making in animals for The Scorpion and the Frog. To learn more, check out Can a Horde of Idiots Be a Genius? and Why This Horde of Idiots Is No Genius.

In case you've been living in a cave lately, the U.S. Government has been shut down since October 1st. Not because of a terrorist attack or a bank system meltdown or a natural disaster, but because Congress cannot agree on a spending bill to determine our government's funding plan for the next year. The government shutdown has its consequences (such as closed national parks, postponed federal research funding, the halting of the CDC's flu vaccine program, and unpaid federal employees), but these will seem like a slap on the wrist if Congress can't agree to raise the debt ceiling by October 17. If we are still in a government deadlock at that point, we will default on our national loans and suffer disastrous consequences (such as the devaluation of the dollar, social security payments not being made, spiking interest rates, and devaluation and forced selling off of bonds). Congress is up against a deadline to make a group decision, and the consequences of not making one in time are much higher than the consequences of making an inperfect one. It's hard to come to a consensus when so many individuals in the group have a strong opinion one way or another, but the fact of the matter is: honeybees can do it. So why can't we?

This honeybee swarm has precious little time to make a democratic decision as to where they will move to. A decision deadlock could have fatal consequences. Image by Nino Barbieri at Wikimedia Commons.

You may think that honeybees can't possibly have to make group decisions as critical or complicated as the ones our government is facing, but you'd be wrong. Honeybees live in swarms of thousands. When the hive becomes overcrowded, about a third of the worker bees will stay home to rear a new queen while the old queen and the rest of the hive will leave to begin the process of finding a new home. During this time, the migrants will coalesce on a nearby branch while they search out and decide among new home options. This process can take anywhere from hours to days, during which the colony is vulnerable and exposed. The consequence of taking too long to make a group decision could be the death of the whole migrant colony. But they can't be too hasty: choosing a new home that is too small or too exposed could be equally deadly.

But within a few days tops, the majority of the scouts still dancing will all share the same vigorous dance (usually for the best quality home option). A quorum has been reached, and the honeybees fly off together to their new home. How do they do that so quickly?

Tom Seeley at Cornell University, Kirk Visscher at the University of California-Riverside, Thomas Schlegel and Nigel Franks at the University of Bristol and Patrick Hogan and James Marshall at the University of Sheffield conducted a series of studies on honeybees to see how they make group decisions effectively and efficiently.

First, the researchers video recorded scout bees returning to the swarm. They observed multiple dance-votes for sites as they had expected, but interestingly, they also observed many scout bees buzzing while butting their heads against a dancer. Dancing bees that received numerous head-butts from other scout bees stopped dancing as a result. But who is doing these head-butts and why?

The researchers hypothesized that the head-butts serve to silence bees with opposing viewpoints. They took hives of bees to Appledore Island, a small island off the Maine coast that not only doesn't have any bees, but also doesn't have any good potential sites for honeybee hives. On this island, the researchers could assure that every bee they observed was from their hive and any nest site a bee voted for was one that they made. They then placed two identical high-quality potential nest boxes on the island for the scout bees to find. When scout bees arrived at one nest box, the researchers painted their backs yellow. Scout bees that arrived at the other nest box were painted pink.

Back at the swarm, the researchers observed that almost every bee that head-butted a dancer was painted with either yellow or pink paint, indicating that this is something that only scout bees do. Not only that, but pink-painted bees were much more likely to head-butt yellow-painted bees and yellow-painted bees were much more likely to head-butt pink-painted bees. Eventually, dancers from one of the two sites predominated and at this phase painted bees of both colors head-butted any bees that were still dancing. The whole swarm prepared their wings for flight and took off for their chosen new home. In this group-decision process, head-butting seems to be the honeybee signal for "shut up!"

The researchers wondered if this head-butting behavior may be beneficial to the group decision-making process. They developed computer models to simulate different scenarios in which a group of individuals attempts to make a decision between two alternatives (called A and B) by influencing one another until a quorum for one of the two alternatives is reached. In one of these, there were four possible interactions between individuals: (1) an uncommitted individual can spontaneously commit to either alternative A or B, (2) an individual committed to either alternative could spontaneously revert to an uncommitted state, (3) an individual committed to either alternative could actively recruit an uncommitted individual, and (4) an individual committed to either alternative could cause an individual committed to the opposite alternative to switch to its side. Under these conditions, the simulation ran effectively when one alternative was clearly better than the other, but when the alternatives were equal it resulted in a deadlock at indecision.

The researchers ran another simulation which was identical to the first, except rather than the fourth possible interaction being a committed individual (to either alternative) causing an individual committed to the opposite alternative to switch sides, the fourth possible interaction became a committed individual (to either alternative) causing an individual committed to the opposite alternative to become uncommitted (something that happens in response to honeybees head-butting dancers for the opposite nest box). This decision-making process enabled the individuals to overcome a deadlock and make a rapid decision when both alternatives were equal.

These studies show that honeybees can make an efficient and reliable group-decision while avoiding deadlock by communicating their information (through dance), communicating the quality of their chosen alternative accurately (coded for in the vigor of their dance), and inhibiting bees with the opposite opinion (by butting them in the head). If the U.S. Congress were to adopt these strategies, they could not only get our government functioning again, but the process would be significantly more entertaining. Or they could just be honest and make their decisions independently.

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Further reading:
Seeley, T.D., Visscher, P.K., Schlegel, T., Hogan, P.M., Franks, N.R., and Marshall, J.A.R. Stop signals provide cross inhibition in collective decision-making by honeybee swarms, Science, 335, 108-111 (2012). DOI: 10.1126/science.1210361.

Seeley, T.D. Honeybee Democracy, Princeton University Press (2010).

Can a Horde of Idiots Be a Genius? and Why This Horde of Idiots Is No Genius on The Scorpion and the Frog

Image Credits:
Bee swarm on a bicycle by Nino Barbieri at Wikimedia Commons.

Figure-Eight-Shaped Waggle Dance of the Honeybee (Apis mellifera) by J. Tautz and M. Kleinhenz from Beegroup Würzburg at Wikimedia Commons.