Is Temperament Destiny?

Studies suggests that introversion and extroversion are physiologically, even genetically, based. The most common way to understand the effects of nature from nurture is to differentiate between identical and fraternal twins. Identical twins comes from the same fertilized egg, thus share the same exact genes. While fraternal twins come from separate eggs and share only about 50% of their genes. From these studies, scientists can reasonably conclude that identical twins have more correlation than fraternal twins in terms of introversion or extroversion, even when raised in a separate household.

Though none of these studies were perfect, heritability statistic shows that #temperament are 40 to 50% heritable. Meaning, on average, in a group of people, half of the variability is caused by genetic factors. The other 50% is from the influence of the world around us, especially our own upbringing.

Low-reactive children raised by attentive parents and safe environment tend to grow up full of energy and high achievers. On the other hand, low-reactive children who grew up with parental negligence or in a bad neighbor hood, say some psychologists, tend to be bullies at school or delinquents.

On the contrary, high-reactive children also influenced by external stimulus but even more so than the low-reactive ones. These children absorbs more learnings from other people’s experiences. However, high-reactive temperament comes with great risk. As David Dobbs explained in his article the Atlantic, “high-reactive types are more like orchids: they wilt easily, but under the right conditions can grow strong and magnificent.” These children are especially vulnerable to life challenges such as divorce, bereavement, or abuse. They are also more likely, among their peers, to suffer from social anxiety and depression. But if raised with good parenting or in a positive environment, as studies show, they tend to have less emotional problems, conscientious, and with more social skills than their low-reactive peers in the same situation.

Dr. Carl Schwartz, director of the Developmental Neuroimaging and Psychopathology Research Lab, Jerome Kagan’s colleague and protégé whose work picks up just where Kagan’s longitudinal studies of personality left off. Kagan followed his subjects from infancy to adolescence but Dr. Shwartz were curious to see what happened to them after. In summary, Dr. Schwartz studies suggest that “the footprint of high- or low-reactive temperament never disappeared in adulthood,” wrote Susan Cain¹. This implies that we can only go so far as to diverting from our innate temperament but we cannot change our temperament completely. As Cain puts it, its the “rubber band theory”, where we have the free will to adopt different types of personality but we can only stretch ourselves so far, because a big chunk of who we are is permanent. It goes to show that the common phrase “just be yourself” has been scientifically proven to be effective and healthy.

Additionally, our amygdala, part of our brains that processes emotions, play an important role in shaping our personalities. When our amygdala process fear, our frontal cortex, responsible of our decision making, tells it to calm down. Its the reason why repetition is effective to lessen our fear. But when our frontal cortex is overwhelmed, our fear takes over. Glossophobia, or the fear of public speaking, can be overcome through sheer repetition and continuous exposure, but even with countless hours of practice, under duress, the frontal cortex may be overwhelmed by the amygdala and the underlying fear will come back to life. This shows that our fears also determine the direction where our personality would lean towards. Our temperament may be used as an indicator of what array of stimuli we might fear for, and how we handle those fears, in turn, may be an indicator of what person we might become.