Hello, I’m Wang Fang. Today’s episode is Episode 20. Before we knew it, the program was nearly halfway through, and Part Two also comes to an end today.

Throughout Part Two, we moved from physiology to genetics, evolution to culture, family to society, proximate to distal causes, and the microscopic to the macroscopic. We introduced the many factors used to explain personality and broader individual and group differences in psychology and behavior. In this final episode of the section, I want to use two examples to see how these factors combine and interact in complex ways around a single topic.

The first example concerns sex differences. One long-running debate about sex asks: are men and women really different?Physically, they certainly appear to be. Men and women differ clearly in average height, external genitalia, secondary sex characteristics, sex-hormone levels, reproductive capacity, and so on. But what about psychology and behavior—for example, personality?

In informal, nonscientific settings, women are often described as “friendly, compliant, passive, emotional, expressive, sociable, sentimental, suggestible, poor at mathematics and science…” Psychologists call these personality traits centered on care, expression, relationships, and dealing with others high communality. Men, by contrast, are often described as “rational, independent, aggressive, dominant, objective, achievement-oriented, highly sexual…” These more active and enterprising traits, emphasizing competence and achievement, are called high agency”（agentic）。

“communality” and “agency. Setting aside these slightly awkward terms, psychologists deliberately avoid the more value-laden labels “masculine” and “feminine” when describing sex differences in personality. Awareness of such differences is widespread. In a classic large-sample study in the 1970s, male and female participants of different ages listed traits and behaviors they believed distinguished the sexes (Broverman et al., 1972). Two findings are noteworthy. First, most participants agreed that men and women differed clearly on more than forty personality traits; second, both male and female participants regarded agentic traits as more desirable than communal ones. Decades later, this pattern remains, though it has weakened（Eagly, 2013; Seem & Clark, 2006）。