PEOPLE WITH A nervous temperament don’t usually get off so easily, Kagan and his colleagues have found. There exists a kind of sub-rosa anxiety, a secret stash of worries that continue to plague a subset of high-reactive people no matter how well they function outwardly. They cannot quite outrun their own natures: consciously or unconsciously, they remain the same uneasy people they were when they were little.
Most of the high-reactive kids in Kagan’s study did well in adolescence, getting good grades, going to parties, making friends. Scratch the surface, though, and many of them — probably most of them — were buckets of nerves. “It’s only the high-reactives who say, ‘I’m tense in school,’ ‘I vomit before examinations,’ ‘If we’re going on a class trip to D.C., I can’t sleep the night before,’ ” Kagan told me. “They don’t like it, but they’ve accepted the fact that they’re just tense people.” Invoking Jungian terminology, he called it the difference between persona (the outer-directed personality) and anima (the inner-directed thoughts and feelings). The persona can be controlled, but the anima often cannot.
Nathan Fox of the University of Maryland says that when the anima erupts in high-risk children, it often takes the form of excessive vigilance and misdirected attention. In the first of his two longitudinal studies of temperament, begun in 1989, he followed 180 children from the age of 4 months and gave them a set of neuropsychological tests when they were between 13 and 15. One test, called the spatial-cuing task, measures vigilance and the ability to disengage attention from a perceived threat. It shows two faces briefly on a computer screen, one on each side — the same face looking threatening on one side and pleasant on the other. The faces fade away, and an arrow appears on one side of the screen, sometimes on the side the threatening face had been on,