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

Cain explains in a note at the end of the book why she uses the terms that she does for personality types. Although psychological researchers have different definitions of introversion and extroversion, as well as the alternative spelling of “extraversion” for the latter, her book uses the cultural notion of the terms rather than a clinical definition. Cain’s framework relies on a long-standing trope of Western culture: the “dichotomy between the ‘man of action’ and the ‘man of contemplation’” (269). Examples of these types in philosophy and literature go as far back as the Bible. The Old Testament presents the story of brothers Jacob and Esau, whose qualities fall neatly into the two personality types. Likewise, thinkers like Aristotle, Hippocrates, Milton, and Schopenhauer describe people in terms of the cultural definitions we still have of introversion and extroversion.

Although Cain originally planned to create her own terms, she stuck with “introversion” and “extroversion” because these terms are so deeply ingrained in society—lay people know just what is being referred to. The field of psychology, however, determines personality traits in various ways, and concrete definitions are not set. One method, which researchers have used since the 1980s, is a taxonomy of the “Big Five” personality traits: conscientiousness, agreeableness, neuroticism, openness to experience, and extraversion—sometimes referred to by the acronym CANOE or, denoting a different order, OCEAN.

The Big Five model was created by conducting factor analysis on descriptions of people’s personalities in surveys and questionnaires to come up with the five trait categories that most descriptive words related to semantically (“Big Five Personality Traits.” Cambridge Dictionary of Psychology, edited by David Matsumoto, Cambridge University Press, 2009, p. 84). In the Big Five framework, the degree of “extraversion” is only one metric by which a personality is described; in addition, other metrics affect whether a person is deemed more introverted or more extroverted. For example, individuals who are less open to experience, highly conscientious, and more neurotic (exhibiting negative emotions like anxiety and depression) would likely simply be labeled “introverted” in the cultural definitions Cain employs in the book.