The brain of an insect isn't very big, but bugs in a swarm are somehow able to make decisions of startling complexity. Bees, ants and cockroaches build labyrinthine hives with thousands of workers performing highly specialized tasks, all done without a foreman or vice president or even a blueprint in sight. How insects manage these feats has been shrouded in mystery.
Insight, however, is now coming from an odd source: robotic cockroaches. Scientists in Belgium spent months building robotic versions of the dreaded vermin and then let them loose in a community of real roaches. The robots not only blended in with their biological cousins, they acted as proxies for the scientists, influencing the roach community's collective decisions to search for the best resting location. The study is to be published in tomorrow's issue of the journal Science. "When you make a robot that behaves like a living organism and both influences behavior and is in turn influenced itself, you've made a big step forward," says Stephen Pratt, a biology professor at Arizona State University who is unaffiliated with the research.
The ultimate goal of the research is to figure out how the simple behavior of individuals gives rise to a complex collective decision. The principle, called emergence, is fundamental to life. What is the relationship between each bee's individual motion and the hive's overall success? How do millions of brain cells give rise to thought? "Anything that helps us better understand the principles of emergence is going to be important," says Pratt. The roach is a good launching point toward these big questions because its social system is simple enough for scientists to study mathematically.
The first step was to build robots that real roaches would accept as their own. Although the robotic bugs don't look much like the real thing, they act like them in two key ways: they naturally head toward dark areas and are influenced by the presence of other cockroaches. And more important, they smell like roaches. They emit the same molecules that roaches use to identify their kin, giving the robots a unique roach smell. "We could see the cockroaches accepting the robot when it had the right pheromones, touching and climbing on it," says José Halloy, a professor of life sciences at Université Libré de Bruxelles and lead author of the study. "They would never climb on the robots that did not carry the right pheromones."
The next step was getting the robotic and biological roaches to cooperate on common tasks. In experiments, the robots (programmed to act like natural cockroaches) would collectively head toward a dark shelter, mimicking the nocturnal behavior of natural cockroaches. That got the researchers wondering: if you program the robo-roaches to make an inappropriate decision and gravitate toward the lighted shelter, would the real cockroaches follow, going against their natural instincts?
They will, it turned out. Many of the biological roaches subdued their natural tendency to prefer dark places and followed the collective to a lighter shelter. But influence turned out to be a two-way street. On occasion, the real roaches were able to override the programming of their machine counterparts and get them to scurry into dark hiding places. Being social creatures, both the robotic and natural roaches were paying attention to and following after the example set by others. "If we change the group's social feedback, we changed the pattern," says Halloy.
For his next act, Halloy may build a robotic hen that chicks would accept as mom. Since hens are natural leaders, Halloy's robo-hens could come to rule the chicken coop, teaching his researchers something about more complex behaviors in the process. Theoretically it would be possible to create a robot that could influence collective decision-making in humans (think of a swarm of commuters heading for a subway exit). To do this, researchers would have to invent a robot that people would accept. Fortunately, android technology isn't there yet.