Hard-Wired for Hierarchy

April 24, 2008 — -- You know you're supposed to act differently around your boss than you do around your colleagues, and if you've ever watched a group of dogs interact, you'll see that they have a social order, too.

There's a "top dog" that's in charge, and the others know their place.

Monkeys and other animals have rules about who does what, too. It's called the social hierarchy. And it has a huge influence on us -- on how we act, whom we spend time with, even where we go and what we buy.

Now, researchers have found evidence that our brains may actually be hard-wired for hierarchy. And in fact, we may be wired to value the "top dog" over the people who rank below us.

To understand how our brains process social ranking, Caroline Zink, a neuroscientist at the National Institute of Mental Health, and her colleagues set out to capture images of the brain while having volunteers play a simple computer game.

The researchers looked for differences in brain activity after volunteers were told they were "superior" or "inferior" to others playing at the same time.

"I actually did the analysis twice because I couldn't believe how strong these differences were," Zink said. "It was striking."

The study, published today in the medical journal Neuron, involved placing volunteers in a special MRI scanner. As each person played the computer game, the researchers were able to see what parts of the brain were most in use. They told the volunteers that someone else would be playing the game at the same time and that the other person was either more- or less-skilled.

The researchers made it clear this was not a competition: Players earned a dollar for each correct response, no matter what the other person did. Although the volunteers were shown a photo of the other player, they were really just playing against a computer.

While some parts of the brain always "lit up" no matter who the volunteers thought was playing, an additional pattern emerged when the players thought their opponent ranked higher than they did.