Kagan often talks about the three ways to identify an emotion: the physiological brain state, the way an individual describes the feeling and the behavior the feeling leads to. Not every brain state sparks the same subjective experience; one person might describe a hyperaroused brain in a negative way, as feeling anxious or tense, while another might enjoy the sensation and instead uses a positive word like “alert.” Nor does every brain state spark the same behavior: some might repress the bad feelings and act normally; others might withdraw. But while the behavior and the subjective experience associated with an emotion like anxiety might be in a person’s conscious control, physiology usually is not. This is what Kagan calls “the long shadow of temperament.”

Temperament is important, but life intervenes. Predisposed doesn't mean predestined - comment of a neurvous baby's father: http://community.nytimes.com/comments/www.nytimes.com/2009/10/04/magazine/04anxiety-t.html?permid=96#comment96