Leadership is an innate quality, according to a fish study that predicted trouble in animal social groups, also human ones, when natural roles are reversed.
Groups tend to perform better with a combination of willing followers and strong leaders, which in most animal species are bolder, more extroverted individuals.
But incentives, like higher salaries for humans, can cause natural followers to become leaders, and scientists have long debated the desirability of such role reversal.
To probe whether natural followers can be turned into leaders and vice versa, a research team studied stickleback fish - a group foraging species known to have bold and shy individuals.
First, they studied the fish in large laboratory tanks for several weeks to separate the leaders from the followers.
Leaders were more prone to leave the deep, covered, "safe" area of a tank and travel through "risky", shallow waters to get to a feeding station.
The fish were then divided into pairs, each with one bold and one shy member, the team wrote in the journal Proceedings of the Royal Society B.
In one experiment, the fish were rewarded with food for displaying their natural behaviour - the leader for initiating a trip and the follower for trailing behind. In a second, they were rewarded for role reversal - the shy fish for each time it initiated a foraging trip and the bolder one for following.
"Our prediction was that bold individuals would perform poorly when forced to adopt the role of follower, considering that they are less responsive to other individuals' behaviour," study co-author Shinnosuke Nakayama of the University of Cambridge's zoology department told AFP by email.
The opposite turned out to be true: leader fish were much quicker to adopt a follower role than the other way round.
"Fish can learn to follow but struggle to learn to lead," said Nakayama of the findings.
"We found that leaders are born, not made," added a study summary.
The role reversal also had an impact on group success.
When incentivised to act against their natural instincts, fewer foraging excursions resulted in both members of a pair being fed.
The team said their findings raised intriguing questions for the broader study of group behaviour.
"Strong positive effects of personality variation are only likely to emerge when members of a group are free to establish their own roles, such that bolder (or, in the human case, more extroverted) individuals can assume leadership," the study suggested.
It would appear to "be better for us to adopt social roles of leader and follower in the way we feel natural", added Nakayama.
