Safety in numbers has pretty much ruled in the animal kingdom. But now researchers are discovering that artificially intelligent robots can change animals' natural instinct to live as a group, prompting them to form new patterns of behavior.

Take the typical three-centimeter- (1.2-inch-) long American cockroach, Periplaneta americana. It tends to live in groups with fellow cockroaches in the darkest shelters available. But could new robotic interlopers alter their age-old way of life? In a word—yes.

Researchers at the Free University of Brussels (U.L.B.) in Belgium, École Polytechnique Fédérale de Lausanne (E.P.F.L.) in Switzerland and the University of Rennes in France, along with other European educational institutions report in Science that when they introduced a few socially integrated autonomous robots (boxy in design but made to smell like the real deal) into cockroach communities, they altered the collective decision-making process and triggered new behavior patterns in the bugs. The findings show that it may be possible to use robots to study and control how groups of animals from insects to vertebrates interact.

Cockroaches may not get much respect outside of laboratory settings, but they were better subjects for this test than ants or bees, because they have less elaborate social structures yet still "produce a collective intelligence," says José Halloy, the senior research scientist at U.L.B who coordinated the project.

Cockroaches do not comparison shop or communicate their preferences to one another when selecting shelter. They will, however, instinctively choose darker over more illuminated areas. They will also use their antennae to feel whether other cockroaches are present. Cockroaches will settle in if a place is dimly lit and well populated. "If three or four cockroaches are together under a shelter," Halloy says, "the probability of one of them leaving drops significantly."

During the five-year study, Halloy and his team introduced a number of robot cockroaches into this natural dynamic to see if they could influence the group dynamic. "In that way, the robots were used as tools to improve our knowledge of biology," he says.

The key was constructing robo-bugs tiny enough to successfully infiltrate cockroach clans. To do this, engineers at E.P.F.L. decided to build robots modeled after American cockroaches, which are generally twice the size of cockroaches indigenous to Asia or Europe. The robots were programmable and ran on a battery that lasted at least four hours. The robots were designed to operate autonomously (without any sort of remote control), to detect the difference between light and dark, and to sense the presence of cockroaches and other robots that came within about four centimeters (1.6 inches) of them.

The hardest part of the experiment, Halloy says, was getting the real cockroaches to accept the imposters. To do this, the team tapped biologists at Rennes to develop a pheromone that would fool the insects (which recognize each other via scents picked up by their antennae) into believing that the robo-invaders were fellow cockroaches. The pheromone was sprayed on a piece of paper wrapped around each bot. "Without that smell,'' Halloy says, "the cockroaches avoided the robots."

Researchers confined the real and faux cockroaches to a circular arena with two shelters, each large enough to house the entire group. The robots were programmed to behave in ways that contrasted with the behavior of normal roaches so that researchers could see if the vermin would follow the robots' lead. When the ersatz insects chose shelters with more light, more than half of the cockroaches abandoned their instincts and joined the robots there.

Halloy says researchers now plan to study the effect of artificial intelligence on a vertebrate animal, in this case chicks. To do this, he says, E.P.F.L. engineers will develop larger chicklike robots that can hear, interpret and respond to real chicks' verbal cues. The robot chicks (the first prototype is due in March) must also be accepted by their peers. One way to do this, Halloy says, is to remove newborn chicks from their mothers within 12 hours of hatching and place them with a robotic surrogate mother and artificially intelligent siblings. No word yet on how closely these robo-chick might resemble the real thing.