Edited by Daisy Yuhas

How different are men and women really? About 30 years ago, if dating guides are any indication, some people assumed vast differences in personality, with Men Are from Mars, Women Are from Venus relationship advice. Today, in contrast, certain communities are pushing back against the idea of binary gender, which presents men and women as separate categories. (A quick reminder: gender—described in terms such as “man,” “woman” and “nonbinary person”—has strong cultural and social components. But sex—sometimes described with adjectives such as “male,” “female” and “intersex”—refers to a combination of biological features.)

Scientists are also taking harder looks at gender, sex and personality. For one, researchers are debating how big the personality differences between cisgender men and women truly are. (These are people who describe themselves as either a man or a woman and say that this gender identity aligns with their sex assigned at birth.) The answer depends on how psychologists measure an individual's characteristics.

For example, a study involving more than 300,000 people in the U.S. who self-identified as either male or female looked both at broad personality traits, such as extraversion and agreeableness, and at more specific aspects of these traits, such as a warm communication style or a tendency to act altruistically. In this sample, researchers found moderate differences between male and female participants in the broad traits but, in most cases, larger differences at the more specific level. Overall, for instance, both male and female people in the study were similarly extraverted (a broad trait). When the scientists looked at specific aspects of extraversion, however, they found that male participants, on average, sought out exciting situations more often than female ones did. And female participants demonstrated higher activity levels than male ones.

To test the most comprehensive set of personality traits to date, our project, ClearerThinking.org, ran a series of 15 studies and conducted analyses on more than 15,000 people. Our analyses are limited to cisgender men and women: 98 percent of the participants in our research identified themselves this way, so we did not have enough data to shed light on the personality traits of nonbinary and transgender people. From the data, we discovered 18 specific self-reported traits that varied between these men and women. Next, we built an algorithm designed to predict a person's gender based on their self-reported scores on those traits, which was accurate 78 percent of the time. That accuracy is high but far from perfect, revealing the challenge of predicting an individual's gender from their combination of traits. Finally, we adapted our study questionnaire—in which people rated how much they agree with statements such as “I laugh aloud” and “I frequently worry”—into an online interactive assessment.

To create the questions for our studies, we cast a very wide net, looking at large personality projects, reviewing the academic literature and crowdsourcing ideas. We ended up testing more than 600 personality questions for gender differences before identifying the 18 traits with the greatest variation between the self-identified men and women in our sample. These traits included not only the broad characteristics that are widely used in psychological research (such as extraversion and agreeableness) but also more specific patterns of thought and behavior, such as how frequently an individual takes risks or their degree of focus on aesthetics. We also double-checked our conclusions by running a final study to replicate the major findings. Ultimately we found no large differences in personality between cisgender men and women on any traits. But we did find small and moderate differences in the 18 personality traits.

The most sizable of these differences was the degree to which cisgender people thought about sex, assessed by asking people to rate how much they agreed with the statement “I often have sexual thoughts when I meet an attractive-looking person” and disagreed with the statement “I do not frequently think about sex.” (This “sex-focused” characteristic, while not linked to major personality traits commonly studied in psychology, nonetheless fits the conception of a personality trait as a pattern in thought, emotion or behavior. It also relates to a concept called sexual preoccupation.) We found that gender could explain about 18 percent of the variation in the extent to which people are sex-focused. Men had a higher average score on this trait than women. There were still plenty of women who had a higher score than most men, however. In other words, individual men and women were highly varied, even though at the group level, men tended to differ from women.

On every trait, there was a substantial overlap between men and women. Yet at the tail ends—where people either strongly agreed or disagreed with the questions we asked them—larger differences emerged. For example, very low compassion was rare in both men and women, but the few people who identified as very uncompassionate were much more likely to be men. This result is consistent with the finding that antisocial personality disorder, which often involves a lack of remorse or empathy, is more common among men than women.

So is there a “man's personality” and a “woman's personality”? Fascinatingly, almost everyone in our study was a mix of “more often seen in men” and “more often seen in women” traits. For any given trait, an individual woman was closer to the overall average for women than the overall average for men just 61 percent of the time. And a man was closer to the average for men than the average for women only 57 percent of the time. Only about 1 percent of men and 1 percent of women had almost entirely “more often seen in men” or “more often seen in women” personality traits.

To test how accurately gender can be predicted from personality, we developed a simple machine-learning algorithm (a computer program that looked for patterns in data regarding which personality traits are associated with being a cis man or a cis woman). We trained our algorithm using results from past study participants, then presented the algorithm with the personality traits of new participants to see how well it could predict their gender. Using just the most predictive trait—being sex-focused—the algorithm could predict a person's gender correctly 69 percent of the time. This result may be impressive to some. But the prediction is far from perfect because some women are much more sex-focused than the average man.

The algorithm's accuracy rose to 78 percent when we allowed it to incorporate all the personality differences at once. That's a big improvement—but for the other 22 percent of people, the algorithm was predicting incorrectly. When we released our quiz to the public, accuracy slipped a bit further to 74 percent. That's still much better than the average human, though: We gave another group of study participants sets of personality traits that, we explained, belonged to particular individuals. Then we asked the participants to predict the gender of those other people using the personality traits. They were correct only 58 percent of the time, hardly better than a coin flip. The quiz is called the Gender Continuum Test, and you can try it yourself on our Web site to see whether the algorithm predicts your gender.

We believe our results shed new light on the size of gender differences in personality. There are, however, some important caveats. First, all our study participants were from the U.S., and given that factors such as culture influence personality and gender, we would be hesitant to extend our conclusions to other communities. Second, our study cannot provide insight into the causes of personality differences—for instance, how much these differences can be explained by environment and culture as opposed to biology. Third, as we noted earlier, we do not have enough data to comment on transgender, intersex or nonbinary individuals. We hope that future research explores these and other dimensions of the personality, sex and gender debate.

Right now our study is a reminder that, on average, cisgender men and women do have some small to moderate differences in how they report their personality, but almost everyone is a mix of traits seen more often in men and seen more often in women. If you try to guess someone's personality from their gender, you'll very often be wrong.