When acetylcholine is secreted it encourages a person to introspect and helps one feel relaxed and content. It also enables a person to concentrate on one particular task like reading books or walking. It is easier to turn inwards when there is no external stimulation.
That is why introverts prefer a quieter environment so that they can experience the reward of acetylcholine, which works better in calmer environments.
Some other studies have found that cortical neurons of introverts and extroverts may respond differently to the neurotransmitter chemicals gamma-aminobutyric acid (GABA) and N-methyl D-aspartate (NMDA). This is an interesting connection because both GABA and NMDA have been linked to anxiety disorders.
4. Difference In Gray Matter
The prefrontal cortex is a part of the brain that monitors a number of activities, like social behavior, abstract thought, and decision making. It is also the seat of personality traits. This region contains gray matter – a brain tissue where most of the brain activity takes place.
Introverts contain a higher amount of grey matter in their prefrontal cortexes as compared to extroverts. Also, introverts have gray matter that’s denser on average than extroverts.
How does this affect behavior?
Introverts find it more rewarding to focus deeply on abstract topics whereas extroverts are all about enjoying the present moment.
In a study by Cornell University scientists, the team of investigators gathered a mixed sample of introverts and extroverts and randomly split these volunteers into two groups. The first group took the stimulant Ritalin, while the second group took a placebo. All the participants then watched a series of videos such as random landscape shots and forest scenes. The same test was again performed after three days without drugs. Researchers measured the subjects’ alertness and demeanor.
Extroverts who’d taken Ritalin were excited watching videos even in the absence of the drug. But introverts weren’t happier or more alert post-video, regardless of whether they’d taken Ritalin or not. The finding is rooted in a crucial difference between the ways introverts and extroverts process feelings of excitement. Extroverts, associate feelings of reward with their immediate environment, whereas introverts tend to associate them with their inner thoughts or may interpret them as anxiety rather than excitement.
5. Differences In Frontal Lobes And Amygdala
One a 2006 study, PET scans of introverts showed more activity in the brain frontal lobes. This brain region is activated for remembering, problem-solving, and planning. Extroverts show greater activity in the brain anterior lobes. This brain region involves external stimulated sensory processing like hearing, watching, or driving.
Some studies showed that the right-hemisphere amygdala tends to be larger in extroverts than in introverts, as does the anterior cingulate cortex—except in female extroverts, whose anterior cingulate cortices are apparently smaller than those of female introverts.
Although many studies have highlighted the anterior cingulate in social error detection, it is not clearly understood how introverts and extroverts process social missteps. Researchers have found that an introvert’s premotor cortex tends to process stimuli more quickly when compared to an extrovert.
6. Introverts Prefer One Type Of The Nervous System More Than The Other
There are two parts of the nervous system- sympathetic and parasympathetic.
The sympathetic side is responsible for the “fight, fright and flight” mode. It prepares the body for action, triggers the release of adrenaline, pumps glucose to the muscles to energize them, and the oxygen levels of the body are increased. The thinking process is temporarily halted and the neurotransmitter dopamine boosts alertness in the backside of the brain.
The parasympathetic nervous system, on the other hand, relaxes muscles, conserves energy and boosts food metabolism. It triggers the release of acetylcholine, which in turn increases blood flow to the front of the brain and keeps it alert.
Besides dopamine, extroverts also need its sidekick adrenaline, to make more dopamine in the brain. So, extroverts are linked with the dopamine/adrenaline, energy-spending, sympathetic nervous system. However, introverts prefer to use the acetylcholine, energy-conserving, parasympathetic nervous system. This is what enables introverts to act calmly and take decisions in a measured way.