Cerebral Hemispheres 2

NEUROSCIENTIFICALLY CHALLENGED

NEUROSCIENCE MADE SIMPLER

Neuroimaging and the Social Ladder

April 24, 2008


Social hierarchies, and the corresponding struggles to move up within them, are ubiquitous throughout the animal kingdom. It is common to observe the attainment of dominant, as well as the relegation to submissive, roles in animal groups. As is so often the case, when we turn our attention to our own species, however, we rarely describe ourselves in such ethological terms as dominant and submissive. To do so causes one to draw an uncomfortably amorphous line between the human and nonhuman kingdom, one that many of us avoid as it has a tendency to tarnish the uniqueness of the human condition, allowing for the propagation of the more comfortable idea that we are separate from “lower” forms of animal life.

But social rank exists, and is as evident in human societies as it is in any other. It affects every aspect of our lives, including our health. A famous study of British civil servants found an inverse correlation between social status and cardiovascular and mental health. This corresponds with numerous animal studies that have demonstrated the detrimental health effects lower social status can result in.

The concept of social hierarchy seems so universal as to suggest it may be an innate behavior, caused by neural architecture evolved specifically to regulate it. A group of researchers at the National Institute of Mental Health (NIMH) investigated this recently using neuroimaging techniques. They were hoping to find areas of the human brain that are activated specifically when assessing social rank, either of oneself or others.

To do so they used an interactive computer game that participants played for a monetary prize while their brains were scanned with functional MRI (fMRI). Throughout the game, a participant would intermittently see the pictures and scores of other players, who they thought were playing simultaneously in other rooms. In reality, the subject being scanned was the only player.

The researchers found a number of brain areas that were activated according to whether the participant felt she was succeeding or failing compared to her imaginary competitors. The reward area of the brain, specifically the ventral striatum, was activated just as highly in response to a rise in comparative ranking among other players as it was to a monetary reward itself, underscoring the importance the participants’ placed on social position. When the participants did worse than a player with an inferior ranking, areas of the brain correlated with emotional frustration were activated more strongly than when they were beat out by an equal, or superior, player. Specific areas of the brain were also activated just in the assessment of other players as they appeared on the screen, before negative or positive results of the game had been achieved. This may involve something of a “sizing-up” process, used to assess potential competition. Additionally, more competitive players experienced increased reward stimulation when they won, but also more emotional pain when they lost to an inferior player.

This supports the concept that our brains are designed to struggle for social dominance, even in a society where pure dominance is relatively rare. It certainly makes sense, however, considering the competitive drives that lie in many of us, and the desperation one can experience when one feels humiliated or reduced in stature. While our competition may be much more subtle than the violent dominance battles of bears, primates, or elephant seals, it still exists, and in a much more palpable way than many care to realize.

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