Are men and women basically the same, or are they fundamentally different? Stand-up comedians love this topic, and researchers do, too.

The Annual Review of Psychology has just published a significant summary of the research that asks this question. The article is called Gender similarities and differences and it’s a comprehensive piece of work, touching on big questions: Are differences between men and women the result of evolution or learning? Are boys better than girls at math? How are we different in terms of aggression or leadership skills?

By the time we get to the end of her article, Janet Shibley Hyde has us convinced that men and women are similar in just about every way. That shouldn’t be such a surprise, she notes. After all, we have 23 pairs of chromosomes and only one of them is different.

Here are just three of the topics touched on in Hyde’s article; follow the link to her work for many more details.

Mathematics

The most famous recent statement about math skills differences between boys and girls came from Larry Summers, who was forced to resign the presidency of Harvard in 2006 after suggesting that women are underrepresented in math and science because they have less natural aptitude for those fields than men.

What do we find if we look at a very large sample of test results? Hyde presents a study of more than 7 million pupils in grades 2 through 11 (approximately ages 7 to 17) in the United States. There were no differences between boys and girls at the same grade levels; 3rd grade girls performed like 3rd grade boys. But this study drew on tests of lower-level math skills. What about more complex skills?

A set of data requiring complex problem solving from 12th graders was studied and it, too, showed no difference between boys and girls. This differed from results seen in 1990 in a study of 3 million pupils, in which there was a difference in complex problem solving skills that favored the boys later in high school. It would seem, Hyde concludes, that over the past 20 years, the girls have caught up.

This change is also important because it shows that differences are not written in our genes. Differences between the genders can change over time.

In fact, international test scores show variation from country to country. In some countries the difference between boys and girls is greater, in others it is non-existent. And when there is a difference, it favors boys in some countries and girls in others.

Mental rotation of 3D objects

One of the skills that can make for a better engineer or architect — two fields in which women are under-represented — is the ability to imagine a 3D object from another perspective. A study in the mid-1980s showed a very large difference in mental rotation skills, favoring boys. In the mid-1990s, another studied showed a somewhat smaller advantage for the boys, but it was still large.

Of course, it is complicated to study these skills and other factors can figure in. Researchers who examine the validity of testing note that boys do better at timed tests than girls. For spatial rotation tests, the timed ones unsurprisingly showed a large benefit for the boys. For tests without time pressure, the advantage for the boys was smaller.

Spatial rotation skills are not usually taught at school, so gender differences might be a result of what kids do outside of school. Experiments that use video games to train subjects to mentally rotate object are successful, and since boys spend twice as much time as girls playing video games, they may be developing their advantage this way.

Training engineering students in spatial rotation skills has led to improved retention of young women. In one case, a training program is given credit for increasing retention of female students from 47% of to 77%!

Self-esteem

If women are going to get ahead in their careers, we sometimes hear, they need more self-esteem. At first glance, the research suggests that there are not big differences between men and women on this point. The difference is small in elementary school, it gets bigger in middle school and high school, but starts getting smaller again in college, and the overall numbers for adults between 23 and 59 showed little variation between men and women.

When different areas of self-esteem are examined, however, differences start to emerge. Males have higher self-esteem when it comes to physical appearance, athletic skills and self-satisfaction — as well as math skills. Women, on the other hand, have higher self-esteem than men in areas such as behavioral conduct and moral-ethical skills.

Gender similiarity

The review article discussed here found strongest evidence that men and women are similar. Professor Hyde sums it up like this:

Domains in which gender differences are small or trivial include mathematics performance, verbal skills, some personality dimensions such as gregariousness and conscientiousness, reward sensitivity, the temperament dimension of negative affectivity, relational aggression, tentative speech, some aspects of sexuality (e.g., oral sex experience, attitudes about extramarital sex, attitudes about masturbation), leadership effectiveness, self-esteem, and academic self-concept.

Even with all these differences, though, we are not identical. There are domains in which the genders differ.

Differences are moderate or large for 3D mental rotation, the personality dimension of agreeableness/tender-mindedness, sensation seeking, interests in things versus people, physical aggression, some sexual behaviors (masturbation and pornography use), and attitudes about casual sex. The bottom line is clear: there is no solid evidence supporting claims that biology can explain differences in the cognitive performance or personality traits of men and women. We’re much more similar than we are different. And where we are different, that can change.

Source: Gender similiarities and differences. Janet Shibley Hyde. Annual Review of Psychology. 2014. 65:373–98.