Gender gaps permeate nearly every aspect of our culture, as everything from comic books to the constitution seems to stress the differences between men and women rather than any similarities between the sexes. It’s hard to walk through a bookstore without being bombarded with advice on decoding the other sex’s cryptic behavior; a few classics are Men are from Mars, Women are from Venus, The Female Brain, and the ever-so-helpful Guys are Waffles, Girls are Spaghetti. Sitcoms, romantic comedies, and action movies all tend to exploit traditional gender roles too: females worry, nag, and primp while males theorize, womanize, and ride to the rescue.

Unfortunately, the actual science behind gender gaps isn’t nearly as clear cut. It’s a miasma of conflicting results, non-replicable studies, and varying effect sizes. And when you think about the complexities involved, it’s no wonder there’s a lot of confusion. Researchers studying gender differences must deal with genetics, physiology, behavior, culture, age, environment, race, and innumerable other variables. Behavior is also extremely sensitive to context, which muddies the waters further. Evaluating and interpreting the differences between men and women is, simply put, no easy task.

Sex itself is complex. We already know that sex in the animal kingdom is a surprisingly fluid concept, and that sex determination is more complicated than a single chromosome. In this third installment of our continuing series on sex and gender, Ars is bringing you some of the more promising research into what—if anything—separates males from females when it comes to behavior.

It’s all too easy to fall back on the clichéd metaphor that men and women hail from different planets, or the popular but sketchy evo-psych claims that trace every aspect of our behavior back to our origins on the African savannah. Here, we’ll steer clear of these overhyped and underwhelming points of view. Instead, we'll take a look at some of the good science that is beginning to separate truth from fiction in regard to gender gaps. Some of this research is creative, some is elegantly simple, and some is complex and nuanced. But these studies are all promising in terms of identifying gender gaps, hinting at their origins, and suggesting how we might use this knowledge in the future.

Beginning at the beginning

Despite the difficulties inherent in studying gender gaps, it’s an important task, because what we know (or think we know) about these gaps actually affects how we behave. Teachers treat and evaluate male and female students differently. Females’ test performance drops when they are told that men generally score better on the test than women. Both men and women tend to fulfill cultural expectations regarding their gender, even when it comes to something as simple as smiling. Our awareness and understanding of sex differences do matter, because—either intentionally or unintentionally—we use this knowledge to inform our behavior and the behavior of others.

The first major question that needs to be asked is whether gender gaps actually exist, or whether they are merely a figment of our collective imagination. Not surprisingly, the evidence is mixed.

A large and rigorous study published recently in PLOS ONE found larger than expected gender differences in personality worldwide, including significant gender-based differences in sensitivity, warmth, apprehension, dominance, and rule consciousness. The researchers calculated an overall overlap of just 10 percent in the distribution of males’ and females’ personalities. That’s a huge difference, in psychological terms.

However, psychologist Janet Shibley Hyde conducted a meta-analysis that challenged the notion that men and women are so vastly different. After evaluating 46 studies of psychological gender differences ranging from cognition to personality to self-esteem, Hyde identified just a few areas in which men and women differed significantly. These include physical aggression, motor skills, and measures of sexuality (such as the frequency of masturbation). But for the vast majority—78 percent—of the traits and behaviors she examined, Hyde found little or no difference between the sexes. Men and women, she argued, are more alike than they are different.

So, no consensus there. And uncertainty is the norm when it comes to research on gender gaps in cognition and behavior. A quick literature search shows that self-esteem does and doesn’t differ between males and females, that men are and are not better at reading maps, and that there are and are not differences in how the two sexes use language and vocabulary.

Depending on the methodology, the context, and the subtleties of the questions being asked, there are very few solid generalizations we can make about gender differences between men and women. There are a few widely-accepted differences: men are more aggressive and more likely to commit crimes than women are, and women are more prone to anxiety and are more likely to be diagnosed with depression than men are.

If evaluating the extent of sex differences seems complicated, the next step is even more difficult: figuring out where gaps originate. Are differences between men and women innate, dictated by our DNA and our evolutionary history? Or are they a product of our culture and the experiences and interactions we have?

A search for the biological roots of gender gaps

At first, the answer seems obvious. To figure out where these gaps originate, start with our brains. And there’s no question that there are biological differences in the brains of men and women; the sexes differ in the size, symmetry, and activation of several major brain regions, as well as the amount of gray and white matter in the brain.

But one of the major stumbling blocks in understanding gender gaps is that “biological” differences aren’t necessarily equivalent to innate, “hardwired” differences. The brain is a malleable organ that changes over time in response to a person’s experiences, exposures, and opportunities. For instance, practicing karate can enlarge part of the brain responsible for motor skills and coordination, and the more a person listens to music, the more sensitive their auditory system becomes. This plasticity is just one of the many reasons why it’s extremely difficult to determine whether there are quantifiable innate differences between the brains of men and women. Differences in brain structure or function don’t necessarily indicate that gender gaps are based deep in our genes or our evolutionary history.

But despite the challenges, researchers have tried to tackle some of these difficult questions. One way to determine whether biology is at the root of a sex difference is to limit the influence of experience as much as possible. By studying the brains and behavior of infants, scientists can try to look at “nature” before “nurture” has a chance to intervene.

A relatively large body of literature suggests that in even very young children, females perform better than males in tests of social cognition (that’s the scientific term for the skills that go along with understanding and relating to other people). Of course, since newborns can’t answer surveys or perform complicated tasks, testing social cognition in infants requires the use of simplified proxies such as eye contact. Females as young as just a few days old tend to make more eye contact than males do, and girls this age are better at imitation than boys are. Another study tested whether infants pay more attention to a face or a mechanical object, such as a mobile. At just 36 hours old, newborns of each gender already have very definite preferences: baby girls show more interest in a human face, while baby boys show more interest in the mobile than the face. At three months of age, females show more expressions of interest, such as wider eyes and raised brows, in response to people than males do.

A group of researchers hypothesized that there may be a genetic component to these sex differences in social skills; they reasoned that females may inherit their social awareness from the paternally-contributed sex chromosome. At first, this seems backwards: if females have better social skills, shouldn’t social awareness be passed on maternally, from mother-to-daughter, rather than paternally, from father to daughter?

But think about it: females normally receive two X chromosomes (one from each parent), while males only inherit a single X chromosome (from their mother). If one of these X chromosomes confers an advantage in terms of social skills, it’s the one from dad that is unique to females, not the one from mom, which both sexes get.

To test this theory, the researchers took advantage of Turner syndrome, a chromosomal disorder in which females have just one X chromosome which can be inherited either from their mother (called Xm, for maternally-inherited) or from their father (called Xp, for paternally-inherited). If social awareness is a product of the paternally-contributed X-chromosome, Xp females should be more socially savvy than Xm females. And that’s exactly what the researchers found: on social awareness tests, Turner females with a paternally-inherited X chromosome greatly outperformed the females whose chromosome came from their mom.