The Chemical Reasoning Behind Introverts And Extroverts

People are very different. People have different preferences, wants, needs, and genetic makeup! Nature and nurture have been a topic scientists have spoken about for many generations. The topic debates whether genetic information and environmental situations have a role in making our personalities. Scientists use studies such as twin studies and brain imaging to conclude how nature (genetics) influences our behavior. 

        Take introverts and extroverts as an example: what makes them so different? Introverted and extroverted personalities are influenced by our brain chemistry, specifically two key neuro transmitters: dopamine and acetylcholine. The balance of these two chemicals results in how a person's brain reacts to stimulation and finds a sense of reward. Dopamine is the “feel-good” chemical in the brain's reward system.

        Extroverts have less sensitive dopamine systems, and it's possible people who are extroverted may have fewer dopamine receptors. Having fewer dopamine receptors means individuals who are extroverted require a higher level of stimulation to achieve the same excitement as an introverted person. This need for higher stimulation leads these individuals to seek out social situations, excitement, and adventures to stimulate their dopamine reward networks. In the case of introverts, these individuals have a sensitive dopamine system resulting in less need of stimulation for a feeling of reward and pleasure. 

        Overstimulation can result in feelings of being overwhelmed, drained, or anxious. This is why introverted people are more inclined to calmer environments. Acetylcholine influences pleasure internally. It is involved with the brain's parasympathetic nervous system that controls rest and digestion. Introverts are greatly connected to the acetylcholine pathway. Due to the connection to this pathway, introverted individuals tend to enjoy introspective activities; and is the reason to believe why introverts feel recharged after alone time.

        Extroverts are the opposite; they are dominated by their dopamine driven sympathetic nervous system. Since extroverted individuals are dominated by their dopamine system, the effects of Acetylcholine can't provide the same sense of reward as social stimulation. Genetics influence our behaviors to a great extent, resulting in differences in behavior based on different genetic makeup and how the chemicals in the brain respond to stimuli.

“Dopaminergic Foundations of Personality and Individual Differences. " National Institutes of Health, 29 Aug. 2014, pmc.ncbi.nlm.nih.gov/articles/PMC4214189/. Bouchard, T. J., et al. "Sources of Human Psychological Differences: The Minnesota Study of Twins Reared Apart. " Science, vol. 250, no. 4978, 1990, pp. 223–28, www.science.org/doi/10.1126/science.2218526