Starting on June 7th 2021 I’m going to be teaching my second seminar on the science of sex differences, an eternal flame in the culture wars and a debate I’ve engaged with myself. I’ll be covering 6 essential topics: sex itself, sex differences in sexuality, sex differences in personality, the development of sex differences, sex differences at work, and an overview of the controversy itself.

See the schedule and buy tickets here.

Here is my Youtube promo for the seminar.

Check out the description and readings for each of the topics below.

Session 1 – Why Sex?

The most efficient way to get your genes into the next generation isn’t to combine genes but to make an identical copy of yourself. But there are very few species that reproduce asexually (without sex). Sex evolved because it keeps mutations and parasites at bay. Females and males are defined by whether they make large gametes (eggs) or small gametes (sperm). In almost all species, the female invests much more in reproduction directly. This causes males to make their own sacrifices by competing for mates.  Considered in its simplest form, female and male just represent two distinct strategies for getting your genes into the next generation. Considering what behavior could help or hinder these distinct strategies is the foundation of all sex differences.

Recommended reading:

Battle of the Sexes in Richard Dawkins’ The Selfish Gene

Further reading:

The Red Queen by Matt Ridley is a whole book about this subject

Session 2 – Sex Differences in Sexuality

From an evolutionary perspective, we should expect some of the largest sex differences in sexuality itself. The costs of sex are much greater for women both because they bear the huge costs of bringing new life into the world and because women are much more likely to get sexually transmitted infections from men than vice versa. This also makes women more selective about their sexual partners. Men have minimal standards for a casual sexual encounter but have much higher standards for longer term relationships. Compared to men, women are much more sexually disgust sensitive, more likely to be asexual, less likely to watch pornography, and much less likely to exhibit paraphilias (e.g. exhibitionism, pedophilia, fetishism).

We can see men and women’s casual sexual psychology very clearly with gay men and lesbians — because gay men’s preferences for casual sex are not constrained by women’s preferences, gay men have many more sex partners than straight men. There is also no equivalent app to Grindr for lesbian women.

Men and women have some similar mate preferences for long term partners; for example, kindness, good health, and intelligence. But, there are also large sex differences in what men and women prefer in mates. One huge sex difference everyone takes for granted is that men overwhelmingly prefer to have sex with women and women overwhelmingly prefer to have sex with men. Sex differences in mate preferences are very consistent across cultures and you can correctly guess if someone is male or female 92.2% of the time by just knowing what they prefer in a mate.  For example, across cultures women value earning potential (or status) much more than men, and men value attractiveness and youth much more than women- as one saying goes “women are sex objects, men are success objects”. 

Recommended reading:

David Schmitt – Would you agree to sex with a total stranger?

David Schmitt and David Buss – Sex Differences in Long Term Mating Preferences

Further reading:

Letitia Peplau – Human Sexuality: How do men and women differ?

Diana Fleischman (me): Most people miss this reason women don’t want casual sex

David Buss – The Evolution of Desire

Session 3 – Sex Differences in Personality

In many ways sex differences in personality reflect the larger strategic differences between male and female. For example, males, who almost always invest less in reproduction, must compete with other males to be chosen by or gain access to females, the higher investing sex. This means human males, like almost all other males, tend to be more risk-taking and physically aggressive than females.

When you look at broad personality factors like introversion and extraversion, sex differences are not very apparent. But when you look at narrower personality factors like warmth or assertiveness (both aspects of extraversion), you see much larger sex differences. Many psychologists have claimed that sex differences in personality are small because there are only small differences in individual characteristics. But this ignores the larger global personality differences between men and women. Compare this to looking at a face. Even though there are only small differences in nose shape, mouth shape and eye shape, we can tell whether a face belongs to a man or a woman with over 95% accuracy. Similarly, just by looking at psychological characteristics clustered together, we can tell whether a personality belongs to a man or a woman with 85% accuracy.

Men and women also differ in forms of mental illness, mood disorders, and disorders of personality — women are more likely to have phobias and depression; men are more likely to be psychopaths and alcoholics.

Recommended reading:

Scott Barry Kaufman – Taking Sex Differences in Personality Seriously

David Schmitt – The Truth about Sex Differences

Session 4 – Where Do Sex Differences Come From?

Scientists have tried to disentangle the influence of nature and nurture on sex differences by looking at sex differences in infants and young children and by looking at natural experiments. Infants only show small sex differences, but this isn’t evidence that these differences are socialized, as is sometimes claimed. Sex differences start to emerge in girls and boys as they practice the skills and socializing relevant to their particular reproductive strategy — for example, rough and tumble play in boys and practicing caretaking behavior in girls. I’ll cover three pieces of evidence that indicate sex differences are not strongly determined by socialization: the tragic David Reimer case study, “guevodoce” boys in the Dominican Republic who are raised as girls until the age of 12 and girls with congenital adrenal hyperplasia, a disorder that masculinizes their psychology in many ways.

Recommended reading:

Sex differences in social development from Male, Female by David Geary

Session 5 – Sex Differences at Work

Women and men have very similar overall cognitive ability, but there are significant differences in many of their aptitudes, interests and attitudes towards work-life balance. Women make up the majority of university graduates and in many places, including the USA, get more advanced degrees than men. And yet, women represent the minority in many areas of science, technology, math and engineering (STEM). The contested “gender equality paradox” points out that women in less egalitarian countries are more likely to end up in STEM, which casts doubt on the idea that discrimination or other systemic forms of sexism account for this disparity. According to Simon Baron-Cohen, women tend to be more “people oriented,” or empathizers, and men tend to be more “thing oriented,” or systemizers. These differences in interests and cognitive strengths leads to women’s overrepresentation in fields like health care and men’s overrepresentation in engineering and finance. Finally, in terms of attitudes towards work, the “Study of Mathematically Precocious Youth” (SMPY), found that unusually mathematically gifted women preferred to work fewer hours and spend more time with family, friends and hobbies than men.  Susan Pinker has warned against judging everyone by a “male model of success” defined by earnings and status.

Recommended Reading:

Sex Differences in Occupational and Vocational Choices from Charles Murray’s* Human Diversity

*If you’ve heard of Charles Murray, you know he’s controversial, but I’ve assigned this because it’s the clearest and most thorough explanation of sex differences in economic behavior I could find.

Further Reading:

Stewart-Williams and Halsey (my highlighted copy at the link) exhaustively details studies implicating both cognitive differences and discrimination possibilities for the sex difference in STEM as well as closely examining many different possible remedies

Susan Pinker – The Sexual Paradox

Session 6 – The Controversy

In 2006, Larry Summers resigned as president of Harvard University after he made comments indicating that women may be less represented in STEM because of group differences in “intrinsic aptitude.” In 2017, debate about sex differences erupted again when James Damore wrote the infamous “Google memo,” which similarly posited that women are underrepresented in technology and leadership because of differences in intrinsic aptitude and motivation. Perhaps inspired by this controversy, Cordelia Fine, an author who wrote, “There are no essential male or female characteristics,” won the prestigious Royal Society book prize for Testosterone Rex (here is a well-balanced critique of the book). In this final seminar, we’ll discuss the culture war around sex differences that’s sure to be with us for a long time.

Recommended reading:

Aurora Sola – The science of sex differences is nothing for feminists to be afraid of

Steven Pinker – Gender chapter from The Blank Slate

Corey Clark and Bo Winegard – The Myth of Pervasive Misogyny

Further Reading:

These two blogs are a really good faith debate between the most prominent scientists on either side of the controversy:

Sex Differences in Brain and Behavior: Eight Counterpoints – Marco Del Giudice, David A. Puts, David C. Geary, and David P. Schmitt

Responding to Ideas on Sex Differences in Brain and Behavior – Cordelia Fine, Daphna Joel and Gina Rippon