The finding, published in the Feb. 3 issue of Nature, helps settle age-old questions about how animals coordinate their actions. Previously, scientists had looked for subtle signals or other explicit systems that animals may use in disseminating information through groups. The new study showed that such complexity is not necessary: Large groups easily make accurate decisions about where to go even when no individuals are regarded as leaders and very few individuals have any pertinent information.

In addition to shedding light on the graceful coordination of animal groups, the results may be useful in understanding how humans behave in crowds and in designing robots that explore remote locations such as the ocean or other planets.

"When you see apparently complex behaviors, the mechanisms that coordinate these behaviors may be surprisingly simple and generic," said Iain Couzin, a postdoctoral researcher in Princeton's Department of Ecology and Evolutionary Biology and lead author of the study.

Using computer simulations, the researchers found that group coordination arises naturally from two basic instincts: the need to stay in a group; and the desire by some individuals to act on their own information about where to go. First, the researchers programmed their simulated animals with a basic urge to stay near others, but not collide with them. This instinct alone caused individuals to form close-knit, evenly spaced groups like those of real animals, which pay a high price -- such as being eaten -- if they stray from their group.

Second, a few animals were programmed to have a preferred direction, as if aware of a food source or other valued destination. These animals were instructed to balance their desire to move toward
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Contact: Steven Schultz
sschultz@princeton.edu
609-258-5729
Princeton University
3-Feb-2005