MANILA, Philippines?Everybody?s doing it?why shouldn?t we??

Variations of the line above are likely familiar to most people. It?s often used to convince the listener that one has to wear the latest fashions from Paris, go to Disneyland, buy a new car or eat at a particular restaurant.

If, as the listener, your first response is to ask just who ?everybody? is, think again. A study in the May 13 issue of the journal of the Proceedings of the National Academies of Science suggests that the question to ask should really be how many people are part of ?everybody.?

Biologists from the Britain?s University of Leicester and University of Leeds teamed up with colleagues from Sweden?s Uppsala University and the United States? Princeton University to find out how members of a group decide if they should follow the leader. Their findings indicate that the decision is based on what other followers before them have done.

Powerful influences

?Social conformity and the desire to follow a leader, regardless of cost, exert extremely powerful influences on the behavior of social animals, from fish to sheep to humans,? said biologist and lead author Ashley Ward, now affiliated with Australia?s University of Sydney.

Blame it on the animal?s innate longing to be part of a group, Ward said. While anyone in the group can choose to be a leader, each individual in the group has to decide if the leader is someone who has valuable information, such as places to go for food or places to avoid because predators lurk there. Ward and his colleagues hypothesized that the animals relied on what they called ?quorum response,? or waiting until a significant number of other group members had made their choice, before giving their own decision.

To test their theory, Ward and his colleagues studied a fish called a three-spine stickleback in groups of 1, 2, 4 and 8 fish at a time. They placed the fish at the end of a Y-shaped maze and placed fake sticklebacks under the researchers? control at the juncture to see if the real fish would follow them. A stickleback predator waited at one tip of the Y-maze; a shaded refuge zone lay at the other tip.

The researchers found that the real fish would follow where the majority of fake fish would lead, even if they ended up facing the predator. Groups of one or two would follow a single fake fish, but groups of four and eight wanted to see at least two fake fish moving in the same direction before following them.

Accuracy of decision making

And in cases where the researchers had two or four fake fish divide into two groups and go down both sides of the Y-maze, they found that the real groups of fish being tested also divided.

?Quorum responses generally improve the accuracy of decision-making,? Ward and his colleagues concluded in their paper. ?By biasing the decisions according to the decisions of others the proportion of errors made is reduced, with larger groups making more accurate decisions.?

Better-informed decision making allows the group to survive, even if a few may stray, the researchers conclude. Studies like this one, they said, could be used not just to understand the behavior of other social animal groups, but also the behavior of human crowds, ?such as stand in the street and stare skyward when there?s nothing to see, just because someone else is doing it.?

(E-mail the author at massie@massie.com.)