Republican presidential candidates (L-R) Ron Paul, Mitt Romney, Rick… (Win McNamee/Getty Images )
Now that Michele Bachmann has dropped out of the race for the GOP presidential nomination, we are left with an array of the usual suspects in American politics — namely a bunch of men who seem to spend much of their lives bragging about how tough they are.
We have Rick Perry waxing macho about the number of executions he's overseen in Texas and Rick Santorum threatening to bomb Iran. There's Newt Gingrich proclaiming that the race is going to boil down to being between "Newt and not-Newt." Even the septuagenarian Ron Paul starts his campaign appearances with Darth Vader's theme music, which he uses to emphasize how dangerous he is to Mitt Romney.
As any zoologist would instantly recognize, what we have here are a bunch of male primates vying for dominance.
What are the attributes of a socially dominant male primate? Scientists who study animal behavior have been looking at that question for a long time, producing some complicated answers. But there was a particularly fascinating insight in a superb recent paper that looked at the brains of socially dominant primates. The paper was published by Jerome Sallet and his colleagues at Oxford University in the journal Science, and the part of their research that was most relevant to our troop of Republicans concerned male rhesus monkeys.
First, you have to understand that male rhesus monkeys are among the least Dalai Lama-esque of primates. They form strict, linear dominance hierarchies, and the highest-ranking guy holds his position through aggression and intimidation, something primatologists call a "despotic" dominance system. Rhesus males are often brutish and combative. (And just to disabuse anyone of the notion that all primates are like rhesus monkeys, there are other primate species in which males hold on to dominance thanks to the collective support of females, others where it's the females who are dominant, others where dominance and hierarchy are irrelevant concepts.)
Sallet and his team studied the behaviors of the rhesus males in different social groups, figuring out the hierarchies. Then, with those behavioral data in hand, the researchers scanned the brains of the monkeys using magnetic resonance imaging to determine the size of different parts of the subjects' brains.
Looking at the brain this way is informative — because size matters. A region that has been working hard tends to increase in size, while those that are mothballed get smaller. Spend a summer learning how to juggle, say, and the part of the cortex devoted to hand-eye coordination expands. Go through a horrific experience that results in post-traumatic stress disorder and you'll probably end up with an enlarged amygdala, a part of the brain that is centrally involved in processing fear and anxiety. Conversely, lose your hearing and your "auditory cortex" will atrophy.
When the researchers scrutinized the monkeys' brains, all sorts of interesting findings popped up. One involved the issue of dominance. After controlling for such factors as age, weight and size of the social group, out popped a clear correlation: The higher a male's rank, the larger the average size of a particular brain region.
Was this a region that controls the muscles required to pummel a rival? Were these the neurons that cause testosterone to be secreted? No and no.
The size increase was in a region far from the world of muscles and androgenic hormones, a region called the rostral prefrontal cortex. This area of the brain has to do with social smarts, with drawing inferences based on information about what other individuals can see, what they know, what they think (something psychologists call "theory of mind"). In humans, people with more gray matter in that region are better at understanding multiple layers of human interaction. They'd be good, for example, at the virtually impossible task of keeping track of who, in "A Midsummer Night's Dream," is in love with whom, and who thinks he might know who is in love with whom. In other words, this is a brain region central to being able to understand someone else's perspective.
A study like this can't tell you whether a big rostral prefrontal cortex causes a male to become high-ranking, whether it's the other way around, or whether it is neither of those things. What it shows is that on average, the size of a part of the brain centrally involved in social intelligence is a good predictor of high rank, a cool and novel finding.
And there is an instructive lesson here for this presidential season. As the candidates vie to show how tough they are on Iran, the national debt and those suffering polar bears trying to foist the myth of global warming on us, we should think about those high-ranking, bully-boy rhesus monkeys and their large rostral prefrontal cortexes. It's likely that politicians too have developed parts of their brain that could be put to better use than feuding and posturing. Perhaps it's time for humans to demand that our leaders use their brains for more than coordinating the muscles responsible for chest thumping.
Robert M. Sapolsky is a professor of neuroscience at Stanford University and the author of "A Primate's Memoir," among other books.