April 25, 2008
Human Brain Appears "Hard-Wired" for Hierarchy
Researchers at the National Institutes of Health have conducted imaging studies that have identified how the brain reacts to social status. They believe that social hierarchies strongly influence motivation as well as physical and mental health and that different brain regions are activated when a person moves up or down a pecking order or views perceived social superiors or inferiors.
To find out, the NIMH researchers created an artificial social hierarchy in which 72 participants played an interactive computer game for money. They were assigned a status that they were told was based on their playing skill. In fact, the game outcomes were predetermined and the other "players" were simulated by computer. While their brain activity was monitored by fMRI, participants intermittently saw pictures and scores of an inferior and a superior "player" they thought were simultaneously playing in other rooms.
Although they knew the perceived players' scores would not affect their own outcomes or reward — and were instructed to ignore them — participants' brain activity and behavior were highly influenced by their position in the implied hierarchy.
The researchers point out that the 'processing of hierarchical information seems to be hard-wired, occurring even outside of an explicitly competitive environment.'
Key study findings included:
* The area that signals an event's importance, called the ventral striatum, responded to the prospect of a rise or fall in rank as much as it did to the monetary reward, confirming the high value accorded social status.
* Just viewing a superior human "player," as opposed to a perceived inferior one or a computer, activated an area near the front of the brain that appears to size people up — making interpersonal judgments and assessing social status. A circuit involving the mid-front part of the brain that processes the intentions and motives of others and emotion processing areas deep in the brain activated when the hierarchy became unstable, allowing for upward and downward mobility.
* Performing better than the superior "player" activated areas higher and toward the front of the brain controlling action planning, while performing worse than an inferior "player" activated areas lower in the brain associated with emotional pain and frustration.
* The more positive the mood experienced by participants while at the top of an unstable hierarchy, the stronger was activity in this emotional pain circuitry when they viewed an outcome that threatened to move them down in status. In other words, people who felt more joy when they won also felt more pain when they lost.
The researchers are planning follow-up studies to explore brain activity in response to the experimental social hierarchy in patients with mental illnesses like schizophrenia or autism, which are marked by social and thinking deficits. The researchers will also be exploring whether particular gene variants might differentially affect brain responses in similar experiments.
Source: NIMH