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Fish choosy about leaders

The Stickleback fish is quite particular about the kind of leader its members choose, a new study has found. Know more...

tech reviews Updated: Nov 14, 2008 15:35 IST

A fish species is quite particular about the kind of leader its members choose, a new study has found.

"Stickleback fish preferred to follow larger over smaller leaders," said Ashley Ward of Sydney University, who was involved in the research.

"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," he added.

"Their consensus arises through a simple rule," said David Sumpter of Uppsala University in Sweden, who led the research.

"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, said an Uppsala University release.

"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," Sumpter said.

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 size.

Now, the researchers find, the same is true in schools of stickleback fish making the decision about which leader to follow.

These findings were published in the Thursday issue of Current Biology.