Areas in the brain size up competition
Reported November 01, 2007
ATLANTA: Humans spend a lot of time sizing each other up a fact long known to social scientists. But a new study has pinpointed the brain areas that appear to be involved in this process of social comparison.
The study, led by Caroline Zink, a postdoctoral fellow at the National Institute of Mental Health, found that several brain regions showed increased activity when people were evaluating their standings in a social hierarchy.
Dr Zink presented the research this month at the annual meeting of the Society for Neuroscience in Atlanta. The question of how people determine their social rankings bears on everything from reality television to high school cliques to personal health.
But Dr Zink said she was puzzled to find that there were no studies of where this might be played out in the brain. “It seemed a little strange because its so influential in everything we do, whether its boss-employee, teacher-student, coach-athlete,” Zink said.
Dr Zink recruited 24 healthy volunteers 12 men and 12 women and had them play a game of skill while their brain activity was monitored by a sophisticated scanner called a fast M.R.I.
The researchers told the participants they would simultaneously be playing two other people: an inferior “one star” player and a superior “three star” player. These other players were invented, however, and their actions carried out by a computer.
To convince the participants that the other players where real, the research team constructed elaborate ruses postponing the start of the game for 15 minutes because another player was running late, for example, or leaving the room under the pretense of helping a player get set up.
The volunteers were asked to press a button as soon as they were given a signal. If they responded quickly enough, they won a dollar. Though the researchers emphasised that the participants were not competing against other players, they also made sure the volunteers saw the scores of the one-star players and three-star players.
The results, Dr Zink said, were astonishingly clear and strong. When the volunteers won more money than the three-star players, raising their status in the game, the brain scanner showed increased activity in three brain regions: the anterior cingulate, an area that has been shown to monitor conflict and resolve discrepancies; the medial prefrontal cortex, which processes thoughts about other people; and the precuneus, a newly discovered region that some scientists think may be the seat of self-consciousness, the brains ability to think about itself.
In contrast, when the one-star players won more money during the game than the volunteers, lowering their status, activity increased in the ventral striatum and the insular cortex, also known as the insula.
“We think the insula is the brain region that gives you that sinking feeling in your gut,” Dr Zink said. “It seems to be responsible for the somatic representation of emotional state.”The insula, located deep in the brain, has been identified by other researchers as a brain region involved with feelings of disgust.
The ventral striatum, another deep brain structure, has been linked in primates to motivation and reward, and scientists have hypothesized that it is part of the neural circuitry that keeps track of progress through learning.
“Im a little bit wary of assigning causality at this point,” said Robert Josephs, an associate professor of psychology at the University of Texas, Austin, who studies the effects of sex hormones on dominance.
Source : NYT news service