Evidenced by numerous number of researches that include Extraversion and introversion are biologically determined by the levels of cortical arousal found in the ARAS part of the brain.
Extraversion and Introversion: A Biological Understanding
Extraversion and introversion depend on the ascending reticular activating system (ARAS)1 part of the brain. Oxford Dictionary defines an introvert as “a person predominantly concerned with their own thoughts and feelings rather than with external things” whereas an extravert is “a person predominantly concerned with external things or objective considerations.” The terms introversion and extraversion were first introduced and popularized by Carl Jung (1921) in his book Psychological Types. In Jung’s book, he explained that introversion and extraversion can be further
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This study supports Eysenck’s theory. ARAS responds to stimuli like food or social contact. Increasing the level of ARAS activity increases the production of saliva. By Eysenck’s theory, introverts should produce more saliva when a stimulus was introduced (lemon) since introverts have naturally high ARAS activity levels (BBC, 2014).
In light of Eysenck’s theory, he further proposed that extraverts will engage in sexual activities earlier than introverts. This theory was supported by Barnes, Malamuth, and Cheek (1984) who assessed college-age men and found out that extraverts acquired sexual knowledge earlier than introverts. Extraverts are more pleasure oriented and sexually interested in wider range of sexual activities than introverts.
Another study (Schenk and Pfrang, 1986) also supported Eysenck. The subjects in this study were young unmarried men. The results showed that extraversion and introversion affect sexual behavior. Extraverts engage in more sexual activities and had intercourse more frequently than