Followers bring out the best in their leaders, and leaders elicit better following skills in their minions, according to a new study of stickleback fish published online today (Jan. 29) in Current Biology.

"Actually having good followers helps leaders get on with their tasks," said Andrea Manica, an evolutionary biologist at the University of Cambridge who led the study. "They were doing more together than they would be doing by themselves."

Manica and his colleagues monitored individual threespine sticklebacks (Gasterosteus aculeatus) for their willingness to leave their safe, weedy cover and venture out into the risky, open waters to feed -- an indication of fish temperament. They then randomly paired fish of varying bravado, and discovered that the daring fish tended to lead and the shy fish opted to follow.



"You find these personality traits that not too long ago we thought were uniquely human, and now they're popping up early in the evolution of vertebrates," Ingo Schlupp, an evolutionary ecologist at the University of Oklahoma in Norman who was not involved in the study, told The Scientist.

Manica's team also found that both leader and follow fish, when paired, responded to each other's movements, which led to stronger leaders, more faithful followers, and, ultimately, greater foraging efficiency -- a phenomenon driven by what the authors call "social feedback." "The behavior you get from the pair is totally different from what you see in individuals, which is the result of this feedback," Manica said.

The same general principles should apply in humans, too. In human economics and management studies, it is well known that leader-follower interactions can greatly impact group dynamics and productivity. "The fundamental rules that lead to compromise and synchronized activities ought to be there [in humans]," Manica said.

The study's "only minor shortcoming," noted Schlupp, is that Manica's team only tested fish duos rather than larger shoals. Still, "there's no reason why [social feedback] shouldn't be happening in larger groups," said Manica. "We started playing with three individuals, and the story doesn't seem very different. The mathematics is just very messy."

A study by Jens Krause of the University of Leeds in the latest issue of Behavioral Ecology validates Manica's findings in somewhat larger groups. Krause created quartets of guppies (Poecilia reticulate) consisting of all bold individuals, all shy individuals, or two of each temperament, and showed that the mixed personality shoal had the greatest foraging success. Together, these studies provide a potential mechanism for maintaining individual-level variation in behavioral traits related to personality, Manica said.

Too many cooks in the kitchen, it seems, can spoil the broth -- or at least the fish soup, in this instance.

Editor's note: Watch out for another story about what threespine sticklebacks are teaching us about evolution in the upcoming February issue of The Scientist.

Image: flickr/Uli1001's photostream

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