27 July 2009

Ants trump humans in decision-making

by Kate Melville

Presenting their findings in the journal Proceedings of the Royal Society: Biological Sciences, US researchers contend that ants can accomplish a task more rationally than humans. The scientists, from Arizona State University (ASU) and Princeton University, explain that it is not the case of humans being "stupider" than ants, rather that humans often make irrational choices when faced with challenging decisions.

"This paradoxical outcome is based on apparent constraint: most individual ants know of only a single option, and the colony's collective choice self-organizes from interactions among many poorly-informed ants," says ASU's Stephen Pratt.

The findings came from an examination of the process of nest selection in the ant, Temnothorax curvispinosus. These ants live in small cavities, as small as an acorn, and are skillful in finding new nesting places. The challenge before the colony was to "choose" a nest, when offered two options with very similar advantages.

What the researchers found is that in collective decision-making in ants, the lack of individual options translated into more accurate outcomes by minimizing the chances for individuals to make mistakes. A "wisdom of crowds" approach emerges, Pratt believes. "Rationality in this case should be thought of as meaning that a decision-maker, who is trying to maximize something, should simply be consistent in its preferences," he explains. "For animals trying to maximize their fitness, for example, they should always rank options, whether these are food sources, mates, or nest sites, according to their fitness contribution. Which means that it would be irrational to prefer choice 'A' to 'B' on Tuesday and then to prefer 'B' to 'A' on Wednesday, if the fitness returns of the two options have not changed."

Typically we think having many individual options, strategies and approaches are beneficial, but Pratt points out that irrational errors are more likely to arise when individuals make direct comparisons among options. "Some strategic limitation on individual knowledge could improve the performance of a large and complex group that is trying to accomplish something collectively," Pratt notes.

Studies of how or why irrationality arises can give insight into cognitive mechanisms and constraints, as well as how collective decision making occurs. Insights such as Pratt's and Edward's could also translate into new approaches in the development of artificial intelligence. "A key idea in collective robotics is that the individual robots can be relatively simple and unsophisticated, but you can still get a complex, intelligent result out of the whole group," says Pratt. "The ability to function without complex central control is really desirable in an artificial system and the idea that limitations at the individual level can actually help at the group level is potentially very useful."

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Source: Arizona State University