Fish choose their leaders by consensus( Just after Americans have headed to ...)

Just after Americans have headed to the polls to elect their next president, a new report in the November 13th issue of Current Biology, a Cell Press publication, reveals how one species of fish picks its leaders: Most of the time they reach a consensus to go for the more attractive of two candidates.

"It turned out that stickleback fish preferred to follow larger over smaller leaders," said Ashley Ward of Sydney University. "Not only that, but they also preferred fat over thin, healthy over ill, and so on. The part that really caught our eye was that these preferences grew as the group size increased, through some kind of positive social feedback mechanism."

"Their consensus arises through a simple rule," said David Sumpter of Uppsala University. "Some fish spot the best choice early on, although others may make a mistake and go the wrong way. The remaining fish assess how many have gone in particular directions. If the number going in one direction outweighs those going the other way, then the undecided fish follow in the direction of the majority."

Sumpter defines consensus as a decision in which all the information possessed by the individuals making the decision is used as effectively as possible. "Usually when talking about our own decision making, we say a consensus is reached if everyone is allowed to present their evidence for a course of action and the decision made reflects the general opinion of the decision makers." That's in contrast to decisions made by one or a very small number of group members, which are likely to reflect only their opinions.

The test for whether a group is reaching its decisions on the basis of consensus originated with the French philosopher Condorcet in the 18th century, Sumpter said. Condorcet justified the jury system by showing that the probability that a majority of independent-minded individuals is correct in a decision between "guilty" and "not guilty" increases with group s
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