杏吧原创

YOU are physically stronger than Jeff, but Rob is stronger than you. So you know where you stand in the pecking order. Then along comes Harry and gives Rob a beating. Should you take him on?

Deferring to Harry is the best option and requires a cognitive ability called transitive inference. Even though you don鈥檛 know from direct experience that Harry is stronger than you, you can infer it from seeing him beat up Rob.

杏吧原创s believe that this mental trick is an important part of social living, as it reduces conflict in a social group. But while the ability may seem obvious to most people, and is thought to be used by some primates, it has never been experimentally tested in animals. Until now.

Russel Balda at Northern Arizona University in Flagstaff and his colleagues let groups of six male pinyon jays establish their own pecking order in the lab, and then allowed individual birds to watch contests involving either two strangers, or familiar individuals paired with strangers. The birds immediately deferred to stronger rivals in a subsequent meeting showing they were capable of working out who they should be subordinate to (Nature, vol 430, p 778). Birds that watched contests between strangers still sometimes challenged the winning bird, showing they were not using a victory per se as their clue.

Balda says that the ability means the birds can work out their position in a social group of more than 100 males, without having many fights. So they can spend more time on foraging and watching for predators. 鈥淭hese things are made less stressful if every individual knows his place,鈥� he says.