You may joke about how committee meetings make you feel brain dead, but our findings suggest that they may make you act brain dead as well," said Read Montague, director of the Human Neuroimaging Laboratory and Computational Psychiatry Unit at the Virginia Tech Carilion Research Institute, who led the study.
The scientists used functional magnetic resonance imaging (fMRI) to investigate how the brain processes information about social status in small groups and how perceptions of that status affect expressions of cognitive capacity.
"We started with individuals who were matched for their IQ. Yet when we placed them in small groups, ranked their performance on cognitive tasks against their peers, and broadcast those rankings to them, we saw dramatic drops in the ability of some study subjects to solve problems. The social feedback had a significant effect," said Montague.
Lead author Kenneth Kishida, a research scientist with the Virginia Tech Carilion Research Institute said, "our study highlights the unexpected and dramatic consequences even subtle social signals in group settings may have on individual cognitive functioning."
"And, through neuroimaging, we were able to document the very strong neural responses that those social cues can elicit," Kishida stated.
The researchers recruited subjects from two universities and administered a standard test to establish baseline IQ. The results were not viewed until after a series of ranked group IQ tasks, during which test takers, in groups of five, received information about how their performances compared to those of the other group members.
Although the test subjects had similar baseline IQ scores - a mean of 126, compared to the national average of 100 - they showed a range of test performance results after the ranked group IQ tasks, revealing that some individuals' expressed IQ was affected by signals about their status within a small group.
The researchers wanted to know what was happening in the brain during the observed changes in IQ expression. The subjects were divided into two groups based on the results of their final rank-the high performers, who scored above the median, and the low performers, who scored at or below the median. Two of every group of five subjects had their brains scanned using fMRI while they participated in the task.
They found that dynamic responses occurred in multiple brain regions, especially the amygdala, the prefrontal cortex, and the nucleus accumbens - regions believed to be involved in emotional processing, problem solving, and reward and pleasure, respectively.
All subjects had an initial increase in amygdala activation and diminished activity in the prefrontal cortex, both of which corresponded with a lower problem-solving ability.
By the end of the task, the high-performing group showed a decreased amygdala activation and an increased prefrontal cortex activation, both of which were associated with an increased ability to solve more difficult problems.
Positive changes in rank were associated with greater activity in the bilateral nucleus accumbens, which has traditionally been linked to learning and has been shown to respond to rewards and pleasure.
Negative changes in rank corresponded with greater activity in the dorsal anterior cingulate cortex, consistent with a response to conflicting information.
Neither age nor ethnicity showed a significant correlation with performance or brain responses. A significant pattern did emerge along gender lines, however. Although male and female participants had the same baseline IQ, significantly fewer women were in the high-performing group and significantly more fell into the low-performing group.