How do we make decisions? Let’s say that we have to choose between Brand X and Brand Y; what’s going on in our brain? Just take a stroll in the cereals isle at the food store and you’ll practically hear the neuronal buzz, (or as we used to say “see the wheels turning” before we knew better), in the agonizing process of making a decision.
Turns out, bees have the same dilemma. Which site should they pick to build their new hive? The brain of the individual worker-bee is not capable of making such a fateful decision. But the whole bee society, pooling its collective brains, does make a decision. How do they do it? If we
knew the answer to that we could compare it to our own brain’s decision-making and see if there is a universal pattern in biology to decision-making.
How do bees “persuade”?
Honeybee swarms are produced in the spring when several thousand worker bees leave their hive with their mother queen to establish a new
Cornell University biologist Thomas Seeley has shown that honeybees possess an inhibitory signal, the stop signal, which is known to reduce waggle dancing and recruitment of foragers to food sources. Bees that have been attacked while foraging produce stop signals upon return to the hive, preferentially targeting nest-mates visiting the same food source. The stop signal is a vibrational signal that lasts approximately 150 milliseconds, has a fundamental frequency around 350 Hz, and is typically delivered by the sender butting her head against the dancer. Dancers usually do not show an immediate response to a stop signal. Rather, an accumulation of stop signals increases the probability that a bee will cease dancing. The stop signal enables a colony to reduce its recruitment to food sources that are perilous.
So it was reasonable to see if the same behavioral pattern is employed in “house hunting”, or selecting a new nest site. In a new paper ( Science Exppress, 8 Dec. 2011) Professor Seeley and his collaborators at Cornell and the University of Sheffield in the U.K., began by making video and sound recordings of nest-site scouts performing waggle dances on 5 swarms. Close-up recordings of 40 dancers on 2 of these swarms (20 dancers per swarm) revealed the use of stop signals, just as in the case of warning against going to perilous food sources.
The way this stop signal is delivered is interesting: Each bee that produced a stop signal followed a dancer for 3 -4 dance circuits before lunging toward the dancer, contacting her with head for 0.25 seconds, and delivering 2 -3 stop signals.
So which group prevails in this dance competition? Turns out that the strength of the inhibition produced by each group of scouts is proportional to the group’s size. In other words, the majority wins, and the implicit assumption is that more scouts would “lobby” for the better site by lobbing stop signals at the competing dancers.
But here is an additional, quite surprising conclusion: from a natural selection perspective, this inhibitory signaling helps ensure that only one of the sites is chosen. This is especially important for reaching a decision when two sites are equally good, It seems that the overriding importance is not so much the correct decision of choosing the absolute best site; it is the importance of reaching a decision, any decision, and thereby maintaining the cohesion of the community. Any political lessons for our dysfunctional leaders?
The human analogy
How is this important to us humans, beyond the political analogy? Neurobiologists have been debating how decisions are made in the brain.
For every situation that requires making a decision there are multiple inputs from multiple neurological circuits, each containing information that bears on the decision, and each vying to have its voice heard, and prevail.(“Should I buy this ice cream? Go ahead! it looks so cool, the day is hot, and you love this chocolate flavor. Don’t do it! Did you see how many calories it has? Aren’t you struggling to keep you weight down?”). Artists, writers, philosophers and composers grappled with the story of Faust and his struggle to make a decision. The poor fella made the wrong decision, and gave us great art as consequence. But I think the essence of the story is not so much about the right or wrong decision, as it is about his struggle to make a decision.
One of the models for decision-making in the brains of primates, called the Usher-McClelland (U-M) model, postulates inhibitory connections between competing circuits, and the circuit sending the most powerful inhibitory signals prevails. (“I don’t give a fig about your calories, so shut up, shut up, shut up”).
Computer modeling lends support to this hypothesis. As the authors note, “The similarities between the decision-making processes in honeybee swarms and in the U-M model are striking. In both, there are populations of units (bees or neurons) that act as mutually inhibitory, leaky integrators of incoming evidence, and in both the choice is made when the integrated evidence supporting one of the alternatives exceeds a threshold” (hence the repeated “shut up, shut up, shut up”).
From brain to society
Taking this model beyond a human brain, I think there are fascinating sociological implications to this study. For instance, consider crowd outsourcing, or ‘wisdom of the crowd” decision-making: how does it work? Does the loudest group silence the more subdued one?
A related question: what are the dynamics of groupthink? Do people fall in line because authority figures are not necessarily more persuasive, but
rather more “inhibitory” of non-conforming ideas?
Fascinating how behavioral patterns in social insects like the honeybee can open the proverbial can of worms when it comes to our individual and social behavior. I think King Solomon said it best 3100 years ago : Go to the ant, you sluggard; consider its ways and be wise! (proverbs 6:6). He selected the ant, another social insect, but still not too bad for somebody who never heard of neurobiology.