In the brain, these thoughts can often be traced to overreactivity in the amygdala, a small site in the middle of the brain that, among its many other functions, responds to novelty and threat. When the amygdala works as it should, it orchestrates a physiological response to changes in the environment. That response includes heightened memory for emotional experiences and the familiar chest pounding of fight or flight. But in people born with a particular brain circuitry, the kind seen in Kagan’s high-reactive study subjects, the amygdala is hyperreactive, prickly as a haywire motion-detector light that turns on when nothing’s moving but the rain. Other physiological changes exist in children with this temperament, many of them also related to hyperreactivity in the amygdala. They have a tendency to more activity in the right hemisphere, the half of the brain associated with negative mood and anxiety; greater increases in heart rate and pupil dilation in response to stress; and on occasion higher levels of the stress hormones cortisol and norepinephrine.
thinkahol * on 19 Aug 11Why are we all so different? Here is a toolkit for finding out what people are really like IN THE 4th century BC, the Greek philosopher Theophrastus, Aristotle's student and successor, wrote a book about personality. The project was motivated by his interest in what he considered a very puzzling question: "Why it has come about that, albeit the whole of Greece lies in the same clime, and all Greeks have a like upbringing, we have not the same constitution of character?" Not knowing how to get at the answer, Theophrastus decided to instead focus on categorising those seemingly mysterious differences in personality. The result was a book of descriptions of personality types to which he assigned names such as The Suspicious, The Fearful and The Proud. The book made such an impression that it was passed down through the ages, and is still available online today as The Characters of Theophrastus. The two big questions about personality that so interested Theophrastus are the same ones we ask ourselves about the people we know: why do we have different personalities? And what is the best way to describe them? In the past few decades, researchers have been gradually answering these questions, and in my new book, Making Sense of People: Decoding the mysteries of personality, I take a look at some of these answers. When it comes to the origins of personality, we have learned a lot. We now know that personality traits are greatly influenced by the interactions between the set of gene variants that we happen to have been born with and the social environment we happen to grow up in. The gene variants that a person inherits favour certain behavioural tendencies, such as assertiveness or cautiousness, while their environmental circumstances influence the forms these innate behavioural tendencies take. The ongoing dialogue between the person's genome and environment gradually establishes the enduring ways of thinking and feeling that are the building blocks of personality. This de
