Now, researchers for the first time have used brain imaging techniques to investigate how people respond to others of higher and lower status. The study suggests that our responses to these hierarchies are hard-wired into our brains.
Psychologists have long been interested in how people respond to status. As far back as the 1950s, psychologist Leon Festinger proposed that people learn and adjust our behavior by constantly comparing ourselves to others.
"It's fairly well established that social hierarchies ... are a strong determinant of social behavior and have enormous impact on health in humans and other primates," said Caroline Zink, a neuroscientist at the National Institute of Mental Health and one of the study's lead researchers. "So it was quite surprising that with technology like fMRI [available], no one had looked at how we process hierarchical information."
In the study, published this week in the journal Neuron, Zink and her colleagues set up a fake social hierarchy based on game skill. The researchers asked people to play a simple computer game that tested response time. Each time they responded fast enough, the participants could win a dollar.
Then the researchers told the participants that two other people would be playing the game at the same time, in rooms next door. Each participant got a few minutes to practice, and then was told that based on the practice score, they had been ranked as a "two-star" player. The other two participants, they were told, had been ranked as "one-star" and "three-star" players.
In reality, the other players were fictional. But the researchers showed the participants a picture of each supposed other player, and used fMRI to measure brain activation as they did. They found that viewing the higher-up, three-star player activated an area called the occipital parietal cortex, which processes attention, and an area called the ventral striatum involved in rewards -- suggesting that the participants paid attention to and "valued" the higher-ranked player more than the lower-ranked one.
The researchers confirmed the findings behaviorally too -- they asked participants to remember details about the other players, such as the color of their shirts, and found that the participants remembered more about the three-star player.
The findings are particularly interesting, according to Zink, because the participants weren't even competing against the fictional other players -- they'd been told that their scores wouldn't affect each other.
"We can see that hierarchical information is so ingrained that it's impossible to ignore, even when we tell them that it has nothing to do with the task at hand," Zink said. "They were very consumed with the information."
Humans aren't the only species that pays attention to status -- in fact, many of our primate cousins are even more obsessed with hierarchy. Duke University neurobiologist Michael Platt has done similar research on rhesus macaques, a type of monkey that lives in large groups organized by social status. In one study, he found that male monkeys were willing to give up a treat -- juice -- in order to look at pictures of higher-status males.
"It's a little counterintuitive, because you'd think that maybe they'd find the higher-status monkeys scary," he said. "But monkeys, kind of like people, can't help but have their attention drawn to the dominant in the group."
In another study, Platt monitored the activity of nerve cells in the monkeys' brains, and found that cells lit up in one of the same attention areas -- the occipital parietal cortex -- as in the new study in humans.
Understanding status in humans is more difficult than in rhesus monkeys, however. Except in some situations, such as the military, social status among humans is much less codified. Many factors -- wealth, age, gender, and others -- may play into people's perceptions of social hierarchy.
One reason the new paper is so interesting, Platt says, is that the researchers managed to create a clearly defined social hierarchy in the lab.
"It's a very clever manipulation that allowed them to create this status," he said.
Understanding how people respond to social status could have implications as far-ranging as public health, Zink and others say. Studies in humans and in other primates have shown that status and anxiety about status, mediated by stress hormones, can contribute to health problems like cardiovascular disease and weakened immune systems.
"While we didn't look at health specifically, these brain regions may include the neuromechanisms underlying the some of those illnesses," Zink said.