Anyone who dreams of a "classless society" may be disheartened by the results of a brain-scanning study reported today: Hierarchical awareness seems to be deeply embedded in the human brain, so much so that there are distinct circuits activated by concerns over social rank.
In the study, a team led by neuroscientist Caroline Zink of the National Institute of Mental Health in Bethesda, Maryland, first set up a "stable hierarchy." Twenty-four adult subjects were asked to press a button quickly whenever a blue circle changed to green. Ostensibly based on their skill at the task, the subjects were assigned a place in a hierarchy containing two other players (who in reality didn't exist). In this part of the study, that rank stayed the same regardless of the subjects' performance, hence the stable hierarchy. Even though subjects were not in competition with other players, they were repeatedly reminded of the hierarchy by photographs of their fictional co-players accompanied by stars indicating their rank.
The researchers then put subjects through a similar experiment, but this time, a person's status changed based on how well he or she supposedly did. That created an unstable hierarchy. In both experiments, subjects got monetary rewards for "correct" button-pushing, which enabled investigators to separate the effects of the monetary reward on brain activity from the effects of changes or threats to social status.
Regardless of the type of hierarchy, subjects' brains were influenced by their place in it. Just viewing a picture of a "superior" player activated an area in the frontal lobe that is associated with making judgments about people. The effect was more pronounced in the unstable hierarchy, with brain regions implicated in emotional processing and social anxiety chiming in.
The study "confirms that our brains are exquisitely sensitive to position in the hierarchy," says epidemiologist Michael Marmot of University College London. "If the hierarchy is stable, we seem to ignore those below us but focus on those higher up. If unstable, and we are in danger of losing status, areas of the brain linked to emotions are aroused."
The authors, reporting in tomorrow's issue of Neuron, say their findings may help explain how brain responses to social status influence health. A U.K. investigation led by Marmot of British civil servants called the Whitehall Study, for example, has revealed that low-status jobholders have worse health than high-status ones, even when researchers control for various lifestyle factors.
Zink and colleagues are planning to conduct similar experiments to see how this brain system operates in patients with a disease such as schizophrenia, which affects social functioning.