...A large number of well done studies have painted a rather consistent picture of sex differences in personality that are strikingly consistent across cultures (see here, here, and here). It turns out that the most pervasive sex differences are seen at the "narrow" level of personality traits, not the "broad" level (see here for a great example of this basic pattern).
At the broad level, we have traits such as extraversion, neuroticism, and agreeableness. But when you look at the specific facets of each of these broad factors, you realize that there are some traits that males score higher on (on average), and some traits that females score higher on (on average), so the differences cancel each other out. This canceling out gives the appearance that sex differences in personality don't exist when in reality they very much do exist.
For instance, males and females on average don't differ much on extraversion. However, at the narrow level, you can see that males on average are more assertive (an aspect of extraversion) whereas females on average are more sociable and friendly (another aspect of extraversion). So what does the overall picture look like for males and females on average when going deeper than the broad level of personality?
On average, males tend to be more dominant, assertive, risk-prone, thrill-seeking, tough-minded, emotionally stable, utilitarian, and open to abstract ideas. Males also tend to score higher on self-estimates of intelligence, even though sex differences in general intelligence measured as an ability are negligible [2]. Men also tend to form larger, competitive groups in which hierarchies tend to be stable and in which individual relationships tend to require little emotional investment. In terms of communication style, males tend to use more assertive speech and are more likely to interrupt people (both men and women) more often-- especially intrusive interruptions-- which can be interpreted as a form of dominant behavior....
