Hello, I’m Wang Fang. At the end of the previous episode we included a Big Five personality test. Did you try it? How did you score on the five traits? Beginning today, we will truly get to know the common currency of psychology: the Big Five.

Before introducing the Big Five in detail, however, I want to explain how this model differs from the categorical models discussed earlier.

First, the “Big Five” refers not to personality types but to personality traits. A trait is never a set of either-or drawers; it is a continuum between two opposing endpoints. Anxiety, for example, lies on a continuum from “never anxious” to “frequently anxious to death.” Traits are continuous rather than discrete, and people are normally distributed along the continuum. Extremely extraverted and extremely introverted people are both minorities; most people are neither very extraverted nor very introverted, and everyone occupies a point somewhere in between. For clarity, our explanations will use the two ends as examples and describe what a typical high scorer and low scorer look like.

Second, although we discuss one trait at a time, all five appear together within one person. Imagine a palette of five colors: everyone paints with all five, but in different shades and intensities, producing a uniquely personal picture. Or imagine five controls on a mixing console: one person turns up two tracks, another turns up the other three, and each ultimately creates a melody unlike anyone else’s. In other words, the overall structure of traits does not vary from person to person; only each person’s level on each trait varies—just as everyone has height and weight but differs in being tall, short, heavy, or slim.

Traits can also interact like chemical elements. Particular combinations of traits at particular levels produce distinctive psychological and behavioral styles, allowing five finite traits to portray millions of different people. Even people with the same traits may possess them to different degrees or combine them differently. These differences are what make the human mind complex, rich, and fascinating.

Now we can formally introduce the five traits that compose the Big Five model: the representative features of each, its distinctive color, and the different behavioral patterns it produces. The first is extraversion.