The Friendly Brain

Is our biology to blame if we're not the sociable type?

There must be something deep in the human soul that makes us blame fate, birth, our parents and all sorts of other things beyond our control for how we turn out, and scientists are no less guilty of this. Case in point: a study published in the European Journal of Neuroscience this week concludes that something about the way the brain develops from birth (or earlier) leads some of us to be people persons—socially gregarious, enjoying the company of others—and some of us to be more aloof.

True, the scientists hedge their bets by making the requisite acknowledgement that people's experience and behavior might act to alter their brain structure, something for which there is ample (and growing) evidence. (My favorites: London taxicab drivers develop a larger hippocampus (that's the site of spatial memory, a good thing to have to navigate London streets) and violin players develop larger somatosensory cortexes in regions devoted to the digits of their fingering hand. But the title of this latest bit of research tells it all: "The brain structural disposition to social interaction." Translation: brain structure comes first, and the result is that you are either a warm, friendly people person who delights in the company of others or a detached, independent, antisocial loner.

The study itself was straightforward. Scientists led by Maël Lebreton and Graham Murray of the University of Cambridge had 4,349 men born in Finland in 1966 fill out a questionnaire that assesses sociability. (The men rated themselves on such points as whether such statements as "I make a warm personal connection with most people" and "I like to please other people as much as I can" describe them.) A high score means a high disposition to social relationships, emotional warmth and sociability called social reward dependence—a people person. A low score indicates a tendency to be socially insensitive and aloof.

The scientists then analyzed MRI scans of the brains of 41 of the men. They found associations between being a people person and the density of gray matter in two brain regions, orbitofrontal cortex (the outer strip just above the eyes) and the ventral striatum (deep in the center of the brain), both known to play a key role in predicting how rewarding something will be. (A high volume or density of gray matter is linked to enhanced cognitive or behavioral function.) "Traits, such as being warm, affectionate, agreeable, sociable, amiable or sympathetic . . . reflect an underlying capacity to experience reward elicited by affiliative stimuli," the scientists write—a capacity, that is, to take pleasure in social situations.

While dutifully admitting that "our study cannot explain the causality behind the associations," the scientists speculate that the extra density of gray matter in regions that find social situations rewarding has its roots in brain development, "ultimately being manifested in a temperament predisposed towards social interaction." In other words, whether or not you're a people person is established long before you so much as lay eyes on other people, that is, before birth. Murray told me by e-mail that his "guess is [that the brain structure differences are] due to genetics, though he adds, "I do think it's possible that, once these areas develop more in certain individuals . . . and then there is more social behavior, this could foster further growth in these regions—a snowball type effect."

The reason the interpretation of such results matters—that is, which came first, the brain structure or the experience and behavior?—can be seen in early reaction to the study. Already Websites are asserting, for instance, that "Ten or twenty years from now this research will lead to the identification of genetic variants for personality types and then the ability to choose these genetic variants for their children."

Really? Why is it not equally likely that this research and the many other studies showing that the lives we lead affect the function and structure of the brain will instead lead to the understanding that the brain we wind up with reflects the choices we make about what we think and do? Thinking in a certain way can alter the pathological patterns of brain activity behind obsessive compulsive disorder (OCD). Meditation can increase the thickness of the brain's cortex. In this case, it seems at least possible that engaging in lots of social activities increases the gray matter in certain regions of the brain, rather than vice versa. Apparently it's a whole lot easier to think that you're stuck with the brain you're born with. It certainly lets you off the hook if, in explaining why you're a social recluse, you can simply say, "My brain made me do it."

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