Biology and How It Relates to Introverts & Extroverts

I recently “revisited” a few of the old ideas within Classical Conditioning. As I am a Psychology major (though still a freshman), I have been taking several classes in Psychology. One of which being Psychology of Learning. In class the other day, we discussed Classical Conditioning and how it relates to introversion and extroversion.

If you don’t know about Classical Conditioning or need a refresher, I’ll give an example of the basic concepts of Classical Conditioning:

In an experimental setting, a researcher will present a dog a stimulus: a bowl of food. The dog will “respond” to the stimulus by salivating at the sight of the food. Then, the researcher will present a new stimulus to the dog: the sound of a bell ringing. A few seconds or so after presenting the bell, the researcher will again present food to the dog (and the dog will salivate again).  After pairing the ringing of the bell stimulus several times with the food stimulus, the dog will begin to salivate merely when a bell is rung. Thus, the researcher has conditioned the dog to salivate at the ringing of a bell.

So, that is Classical Conditioning. Teaching a subject to respond to a stimulus a certain way after several pairings of two stimuli.

I learned in the class that introverts are much easier to condition than extroverts. Introverts are more perceptible to outer stimuli and quite easily respond to the stimuli, whether in behavior or in a reaction like through being startled. This makes a lot of sense really, as introverts are more sensitive to outer stimuli than extroverts.

In Susan Cain’s book, Quiet, she describes a study where five hundred four-month-old infants were tested to see how they reacted to varying noises and moving objects. 20 percent of these infants cried and pumped their arms and legs. 40 percent were quiet, moving their arms and legs occasionally, but they did not exhibit “dramatic limb-pumping”. The other 40 percent were spread out in between these two extremes: the “high-reactive” and the “low-reactive”.

As the researcher, Jerome Kagan, followed these children throughout several intervals of their lives, Kagan predicted that the arm-pumping infants would turn out to be introverted individuals, while the low-reactive infants would lean towards more extroverted temperaments. His hypothesis was correct. After several years of such testing, he found that many of the high-reactive children possessed introverted temperaments, while the low-reactive children had extroverted temperaments.

The amygdala is the organ in the brain that controls much of an individual’s emotions. After receiving information from the sense, it tells the nervous system how to respond.

Kagan hypothesized that infants with an excitable amygdala would react more to external stimuli, and he was right.

As Cain states, “The more reactive a child’s amygdala, the higher his heart rate is likely to be, the more widely dilated his eyes, the tighter his vocal cords, the more cortisol (a stress hormone) in his saliva-the more jangled he’s likely to feel when he confronts something new and stimulating.”

Many of these infants would grow up still high-reactive, but they wouldn’t react to novel sounds and spinning mobiles, they would react to new people, the first day of school, crowds, and any other novel stimuli.

These high-reactive individuals with an excitable amygdala  are what we know to be introverts. It doesn’t take much for an introvert to be stimulated. New classes, being in the middle of crowds, upcoming tests can easily disrupt an introvert’s emotional stability. Going to a party around novel situations and new people can easily drain an introvert, putting an introvert’s amygdala on the fritz trying to react to every little novel stimuli going on. Introverts would much rather stay home, where there is no novel stimuli. Home is familiar. Quiet. Of course, no novel stimuli can be boring, but a book and a cup of tea is enough to satisfy a bored introvert.

The low-reactive individuals with a less excitable amygdala are extroverts. It takes a lot for an extrovert to be stimulated. An extrovert’s amygdala does not react to every little, new, novel stimuli around the extrovert as much as an introvert’s does. Extroverts crave going to parties and amusement parks where there is enough novel stimuli to satisfy a bored extrovert. A book can be interesting to an extrovert, but the extrovert enjoys more extreme, “louder”, salient stimuli.

Being home with no novel stimuli will be boring to both an introvert and extrovert. Sure, the familiarity of home is comforting to the sensitive introvert, but really, we all have been bored at home with nothing to do after a while.

Familiarity is relieving to the introvert, but to satisfy their amygdala, a little stimuli like a movie, book, game, and cup of tea will be enough.

The extrovert’s less excitable amygdala needs much more to be stimulated and going to the party will be enough novel stimuli to make an enjoyable day for the extrovert.

The introvert, however, will be frazzled by overwhelming new circumstances like being around too many people in a noisy environment.

While there is much more to introversion and extroversion than just the biology of the brain, as nature and nurture both equally affect an individual’s temperament, the amygdala does play a powerful role in determining whether a person is introverted or extroverted.



Quiet: The Power of Introverts in a World That Can’t Stop Talking


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s