The long shadow of temperament

In the cognitive neurosciences, temperament is a multilayered concept. It is often defined as a person’s characteristic way of responding emotionally and behaviorally to external events. These responses are fairly fixed, innate, and observable soon after birth and may have genetic components. Personality is defined as not being so immutable. It is shaped primarily by the parental and cultural factors into which a child is born and raised.

Personality is influenced by temperament, the same way a house is influenced by its foundation. Many researchers believe temperament provides the emotional and behavioral building blocks on which adult personalities are constructed.

There is some real controversy about the edges of these definitions, of course—conflicts typical of the “nature/nurture” battlefields researchers have been fighting for decades. Jerome Kagan was really the first to sink some empirical teeth into an argument previously based on opinion. He screened 400 kids way back in 1979, doing experiments in places similar to the rooms in which the 6- and 9-year-olds mentioned above were playing. He found about 15% were behaviorally ebullient, or low-reactive [LR] and another 15% acted like behaviorally inhibited, or highly reactive [HR]. He measured a subset 5 years later and found things were remarkably stable. Only 3% of the children had actually changed categories.

Kagan next investigated 500 kids starting at 4 months of age, coding them using the same LR or HR behavioral algorithms as before. He retested these same kids at 4, 7, 11, and 15 years (the experiment is still ongoing, although Kagan has retired and bequeathed the work to another colleague). He found that HR babies were 4 times more likely to be behaviorally inhibited by age 4. By age 7, some form of anxiety had developed in half of these kids, compared with 10% of the control HRs (who made up about 20% of the population).

As HR kids navigated through school, Kagan noticed most were academically successful, even if they were a bucket of nerves. They got good grades and made lots of friends. They were less likely to experiment with drugs, to get pregnant, or to drive recklessly—perhaps because of an anxiety-driven need to acquire compensatory mechanisms to socialize properly. Kagan actually liked HR people and regularly employed them during his research career. “I always look for high reactives,” he told The New York Times in 2009. “They’re compulsive, they don’t make errors, they’re careful when they’re coding data.”

Kagan’s conclusion? Babies come into this world with an inborn temperament. About 20% are born with a predisposition to anxiety—a behavioral type that remains remarkably stable over time. Kagan calls this the long shadow of temperament.

Not every brain state sparks the same behavior. Nor do they say everything there is to know about temperament. Kagan freely admits he is only studying 1 dimension of the phenomenon—the reaction to new things. At least 6 different dimension scales have been cited by researchers in the field at various times to describe this multidimensional idea, ranging from fearful distress to attention span/persistence to rhythmicity. (For the complete list, see the Figure.)

Most important, these studies make conclusions about tendencies, not destinies. Even when the trends are strong, the predictive power of Kagan’s work runs in 1 direction. The data do not forecast what these children will become as much as they predict what they will not become. HR infants will not grow up to be exuberant, outgoing, bubbly, or bold.

This post is made up of excerpts from the brilliant Dr JOHN MEDINA article in the March issue of the Psychiatric Times. More information, including research into the less ambiguous molecular and genetic sciences behind the findings above can be found here.