We tend to use the words “sex” and “gender” interchangeably, but they are in fact two different concepts. For many, their sex and gender are aligned, but for others, they are not.
Sex refers to biological differences (chromosomal, hormonal, reproductive), whereas gender refers to socially constructed roles, behaviors, activities, and expectations associated with femininity and masculinity.
| Sex | Gender |
|---|---|
| Biological status: chromosomes, hormones, and reproductive anatomy | Socially and personally organised roles, behaviors, and identity |
| Categories: male, female, or intersex | Categories: cisgender, transgender, nonbinary, agender, genderfluid, and more |
| Typically assigned at birth | Can be affirmed, explored, or changed over the lifespan |
| Rooted in biology (nature) | Shaped by culture and upbringing (nurture) |
Sex
Sex refers to the physical and biological aspects of an individual, including chromosomes, hormones, reproductive anatomy, and secondary sex characteristics. Doctors typically assign sex as male or female at birth, based on external genitalia.
Some infants are born intersex: their sex traits do not consistently align as typically male or female (see Intersex, below).
Female
A person whose sex is female typically has two X chromosomes, the hormones estrogen and progesterone, a vulva, a uterus, a vagina, and ovaries.
They also tend to display secondary sex characteristics such as breast development, body fat, oily skin, acne, a higher-pitched voice, and widened hips.
Male
Male-assigned individuals typically have one X and one Y sex chromosome, higher levels of testosterone, a penis, a scrotum, and testes.
They also tend to display secondary sex characteristics such as hair growth, oily skin, acne, body odor, a deepened voice, wider shoulders, and more lean muscle mass.
Intersex
Intersex refers to those individuals who cannot be categorized as male or female across all traits. This could include variations in sex chromosomes, external genitalia, or reproductive organs.
While intersex babies are usually assigned as male or female at birth, they might identify with another gender identity or as non-binary later in life.
Psychological Sex Differences
Are men and women really as psychologically different as stereotypes suggest? The evidence might surprise you. Researchers have tested this directly.
The Gender Similarities Hypothesis (Hyde, 2005)
Aim: Psychologist Janet Hyde tested whether the popular assumption that men and women are psychologically very different actually holds up.
Method: Hyde (2005) combined 46 published meta-analyses, covering hundreds of individual studies on variables such as mathematical ability, verbal ability, self-esteem, leadership style, and aggression. Each meta-analysis produced an effect size, called Cohen’s d, showing how large the average male-female difference was.
By convention, a small effect is about 0.2. A medium effect is 0.5, and a large one is 0.8.
Results: The pattern was striking. Of 128 effect sizes examined across the meta-analyses, 78% were small or close to zero. The clearest exceptions were motor performance, some aspects of sexuality, and physical aggression, which showed moderate to large differences.
Conclusion: Hyde concluded that men and women are similar on most psychological measures. They are not fundamentally different. Within-sex variation usually exceeds the difference between the sexes.
Not every difference vanished, though.
A few areas did show larger, more consistent differences. Motor skills such as throwing distance and throwing velocity showed some of the largest gaps, alongside certain aspects of sexuality and physical aggression. Mental rotation, a spatial reasoning skill, showed a moderate difference favoring males.
Why the Similarities Matter
Later research has largely confirmed Hyde’s findings. Zell, Krizan, and Teeter (2015) pooled 106 meta-analyses covering more than 12 million participants. They reported an average effect size of about 0.21, again pointing to broad psychological similarity between men and women.
The take-home message is simple.
Stereotypes about how men and women “naturally” think or behave often overstate real differences. That gap is usually smaller than assumed. Applying a group average to any one individual is usually a poor guide to what that person is actually like.
These findings have real consequences. Because most psychological traits overlap heavily between men and women, aiming advice at “boys” or “girls” as whole groups is hard to justify. Individual differences usually matter more than group averages.
Even for the traits with the largest sex differences, the two groups still overlap substantially.
Gender
Gender refers to the socially constructed roles, expectations, and behaviors that are often ascribed to the different sexes.
According to the American Psychological Association’s (2015) guidelines for psychological practice with transgender and gender nonconforming people, gender identity is defined as follows:
“A person’s deeply-felt, inherent sense of being a boy, a man, or a male; a girl, a woman, or a female; or an alternative gender” (APA, 2015).
Gender isn’t binary. It exists on a broad spectrum and can shift over time.
The gender category someone identifies may not match the sex they were assigned at birth. Gender identities can include cisgender, nonbinary, agender, genderfluid, or transgender.
There are many ways outside of these identities which a person may define as their own gender.
- Cisgender: Someone whose gender identity matches the sex they were assigned at birth.
- Transgender: Someone whose gender identity is different from the sex assigned at birth. Some, but not all, transgender people also identify as nonbinary.
- Nonbinary: Someone who identifies beyond man or woman, or as neither male nor female.
- Agender: Someone who does not identify with any gender.
- Genderfluid: Someone whose gender identity fluctuates over time.
- Gender Non-Conforming: When a person’s appearance, behavior, interests, or self-concept vary from the norms typically expected of their biological sex.
Gender Expression, Identity, and Roles
People identify and express their gender in a variety of ways. Your gender identity is how you feel inside about your own gender. Gender expression refers to how a person chooses to present themselves to the outside world.
This could include one’s name, pronouns, clothing, haircut, voice, or mannerisms. Gender can also refer to the socially constructed characteristics of women and men.
This could include norms, roles, and relationships with others. Gender roles are largely based on society and culture. Gender identity and expression originate from ideas about which traits and roles are perceived as masculine or feminine in a particular culture.
For example, in Western cultures, stereotypically feminine traits include nurturance, sensitivity, and emotional vulnerability, and stereotypically masculine traits include self-confidence, aggressiveness, and competitiveness.
The David Reimer Case: Nature Versus Nurture
One of psychology’s most influential tests of whether gender identity is shaped purely by upbringing came from an accidental case in Canada. In 1966, an eight-month-old boy lost his penis during a botched circumcision. The injury was devastating.
His parents were referred to psychologist John Money, who believed gender identity was neutral at birth and shaped by upbringing. The boy was surgically reassigned as female, renamed, and raised as a girl from infancy.
Researchers Milton Diamond and H. Keith Sigmundson later followed up when the patient reached adulthood (Diamond & Sigmundson, 1997). The results were striking.
They found that “Brenda” had never settled into a female identity. She felt like a boy throughout childhood. At 14, told the truth, he chose to live as a male again.
The case does not settle the nature-nurture debate on its own; it is a single, unreplicated example. It does show that gender identity is not endlessly changeable by upbringing alone, as the Reimer twins case study explores in full.
What is gender conformity?
Gender influences the way people perceive themselves and each other, how they act and interact. Gender being socially constructed means that gender roles often appear when humans live in groups together and thus, they can vary from culture to culture.
In many Western cultures, there are two widely recognised genders: men and women. These cultures also have gender ‘norms’, which are ideas about how women and men are expected to be and act.
For instance, women in certain cultures are thought to be caring and maternal, whereas men are thought to be stronger and more assertive.
The concept of gender conformity is based on these gender norms. If someone is gender conforming, it means they subscribe to the gender norms expected of their biological sex.
The term gender conformity is rarely used, because almost no one conforms to gender norms 100% of the time. Most people conform in some ways but subvert them in others.
For instance, a gender norm in many cultures is that women should stay home to raise children rather than work. Today, more women work, so this norm no longer holds as strictly as before.
Historically, people have attributed gender roles to biological differences between men and women. Gender roles emerge from the interaction between individuals, their environment, and what behavior a culture expects based on a person’s sex.
Society defines gender roles according to its beliefs about the differences between the sexes.
Below are some ways in which men, women, girls, and boys are often described in many cultures:
- ‘Men are the leaders’
- ‘Women are nurturing’
- ‘Men are more aggressive’
- ‘Women are emotional’
- ‘Girls like pink’
- ‘Boys like blue’
- ‘Girls wear dresses’
- ‘Boys don’t cry’
Issues with gender roles
Once a child’s sex is revealed as a ‘boy’ or ‘girl’, society often places them in one of two gender boxes. These boxes are norms about how they should look, dress, and behave based on that sex.
Boys are typically dressed in blue and given toys like cars. Girls are dressed in pink and given toys like dolls. These patterns feel ‘normal’ within a culture.
Gender roles can be harmful. They pressure people to act according to their biological sex rather than their own choices, and can limit what a person feels able to do.
Breaking from these norms carries a real risk of bullying, criticism, or even violence in extreme cases.
Impact on Women and Girls
Gender roles limit women in specific, well-documented ways.
Many cultures expect men to be more assertive than women, and women who break this norm often face social costs. When a woman acts assertively, she may be criticised. She is seen as not conforming to her expected gender role.
Gender roles can make women feel unable to put themselves forward for a job or promotion they are qualified for. This often happens when men usually hold that position. They may also fear being labelled bossy or undermined by colleagues if they take on a leadership role.
This shows up in the workplace too.
Girls who assert themselves may be told ‘girls shouldn’t talk that loud’ or ‘girls should be quiet and polite’. These messages can leave women and girls with fewer opportunities for success.
Impact on Men and Boys
Gender roles limit men in specific ways too.
A man who dresses in typically feminine clothing, such as makeup or a dress, may be ridiculed for it. He may also feel restricted in what he can wear more generally.
Men may also feel unable to express their emotions. They fear appearing too feminine or being criticised by others.
Boys are often told ‘boys shouldn’t cry’ and that they should ‘man up’ instead of talking about their emotions. This can stop men from expressing or discussing their problems.
Suppressing emotion this way can damage men’s mental health in serious ways. Men who follow this norm may be less likely to seek help for a mental health problem. This raises their risk of suicide.
These norms are often deeply ingrained, so people who don’t conform can be seen as strange or targeted for abuse. Some are forced back into their expected roles to avoid this treatment, which can cause lasting unhappiness.
Key Takeaways
- Sex vs. Gender: Sex is a biological status (chromosomes, hormones, anatomy); gender is the socially and personally organized roles and identity layered on top of it.
- Not Always Aligned: For most people, sex and gender identity match (cisgender), but for transgender and nonbinary people they do not.
- Intersex: Some people’s biological sex traits don’t fit neatly into male or female categories.
- Gender Is a Spectrum: Gender identities include cisgender, transgender, nonbinary, agender, and genderfluid, among others.
- Nature and Nurture: The David Reimer case shows that gender identity is not endlessly shaped by upbringing alone.
- Psychological Similarity: Meta-analyses show men and women are alike on most psychological traits; large differences are the exception, not the rule.
Sources
American Psychological Association. (2015). Guidelines for psychological practice with transgender and gender nonconforming people. American Psychologist, 70(9), 832–864. https://doi.org/10.1037/a0039906
Diamond, M., & Sigmundson, H. K. (1997). Sex reassignment at birth: A long-term review and clinical implications. Archives of Pediatrics & Adolescent Medicine, 151(3), 298–304. https://doi.org/10.1001/archpedi.1997.02170400084015
Hyde, J. S. (2005). The gender similarities hypothesis. American Psychologist, 60(6), 581–592. https://doi.org/10.1037/0003-066X.60.6.581
Stoller, R. J. (1964). A contribution to the study of gender identity. The International Journal of Psychoanalysis, 45(2-3), 220-226.
Zell, E., Krizan, Z., & Teeter, S. R. (2015). Evaluating gender similarities and differences using metasynthesis. American Psychologist, 70(1), 10–20. https://doi.org/10.1037/a0038208
