The Nature-Nurture-Nietzsche Newsletter

In Case You Missed It…

When it comes to politics, confidence and competence don’t always go hand in hand. In fact, often they go in opposite directions: The people with the least political knowledge are the most confident that they’ve got everything figured out - as shown in the figure below. (FOK = feeling of knowing; CJ = confidence judgments.)

Relationship Between Political Knowledge and FOK and CJ Bias. Panel A: Scatterplot showing FOK bias as political knowledge increases. Panel B: Scatterplot showing CJ bias as political knowledge increases. Source: Fulton et al. (2026).

The figure comes from a paper by Erika Fulton and colleagues. Here’s the abstract:

Accurate metacognition is essential to informed political decisions and preventing the spread of misinformation, but research on metacognitive monitoring of political facts, outside of misinformation studies, has not met metacognitive research measurement standards. We addressed this limitation and assessed potential factors (political knowledge, political orientation, and cognitive style) related to this type of metacognitive monitoring accuracy. A sample of 216 Amazon Mechanical Turk participants completed measures of political orientation, political knowledge, and cognitive style, along with a test of political metacognitive monitoring accuracy, between February 2021 and March 2022. Participants were generally overconfident in their political knowledge, especially those with less political knowledge and who were more conservative, with conservatives also showing worse relative metacognitive accuracy. Cognitive style partially explained differences due to political orientation. Our participants were U.S. residents and disproportionately White, male, and lower-to-middle income, so studies of other samples and political contexts are needed for generalizability. Results also build on cue theory, showing that political knowledge and political orientation can act as metacognitive judgment cues. The study highlights the need to improve political metacognitive monitoring accuracy and reveals three targets for intervention: political knowledge, political orientation, and cognitive style.

You can access the paper here or request a free copy here.

Follow me on Twitter/X for more psychology, evolution, and science.

How You Can Support the Newsletter

This post was free to read for all. If you like what I’m doing with The Nature-Nurture-Nietzsche Newsletter, and want to support my work, there are several ways you can do it.

Like and Restack: Click the buttons at the top or bottom of the page to boost the post’s visibility on Substack.
Share: Send the post to friends or share it on social media.

Upgrade to Paid: A paid subscription gets you:
- Full access to all new posts and the archive
- Full access to excerpts from my forthcoming book A Billion Years of Sex Differences
- Full access to exclusive content such as my “12 Things Everyone Should Know” posts, Linkfests, and other regular features
- The ability to post comments and engage with the growing N³ Newsletter community

If you could do any of the above, I’d be hugely grateful. The support of readers like you helps keep this newsletter going and growing.

Thanks!

Steve

Should We Trust Social Science Research?

Steve Stewart-Williams — Tue, 07 Apr 2026 10:07:11 GMT

Photo by Markus Spiske on Unsplash

The Nature-Nurture-Nietzsche Newsletter

In Case You Missed It…

As a reader of The Nature-Nurture-Nietzsche Newsletter, you’ve no doubt heard of the replication crisis: the finding that only around half of studies in the social sciences replicate. Well, here’s a question for you: Is that finding itself replicable?

A massive new study by Andrew Tyner and colleagues, published in the journal Nature, addresses that thorny question, and comes to a strong conclusion: Yes.

The researchers attempted to replicate 274 findings drawn from 164 papers published between 2009 and 2018, spanning 54 journals across the social and behavioral sciences. The replication studies were well-powered, with a greater than 99% chance of detecting the original effect if the effect were real. The team used the original materials wherever possible, and the replication plans were peer-reviewed in advance. In short, this was about as careful and systematic a replication effort as you could hope for.

What did they find? The headline result is that only around 55% of the original results held up. Not only that, but among those that did replicate, the effect sizes were notably smaller in the replications - roughly half the size of the originals.

Different fields showed somewhat different replication rates. As the graph below shows, education was in first place, with economics bringing up the rear. My own field of psychology fell somewhere in the middle of the pack. That’s not much of a boast, though, given that there’s only about a 50% chance that any given psychological finding will replicate.

Source: Sánchez-Tójar et al. (2026).

On the one hand, this is somewhat depressing news. On the other, we shouldn’t forget that some findings in psychology are as solid as anything else in science. As I argue in the essay linked below, not everything you were taught in intro psych was false!

10 Highly Replicable Findings from Psychology

Psychology’s Reputation Problem…

a year ago · 86 likes · 15 comments · Steve Stewart-Williams

You can access the Tyner paper here.
You can request a free copy here.
In a few weeks, I’ll be publishing a piece on the Top 10 most replicable findings from behavior genetics. Stay tuned!

Follow me on Twitter/X for more psychology, evolution, and science.

How You Can Support the Newsletter

This post was free to read for all. If you like what I’m doing with The Nature-Nurture-Nietzsche Newsletter, and want to support my work, there are several ways you can do it.

Like and Restack: Click the buttons at the top or bottom of the page to boost the post’s visibility on Substack.
Share: Send the post to friends or share it on social media.

Upgrade to Paid: A paid subscription gets you:
- Full access to all new posts and the archive
- Full access to exclusive excerpts from my forthcoming book, A Billion Years of Sex Differences
- Full access to exclusive content such as my “12 Things Everyone Should Know” posts, Linkfests, and other regular features
- The ability to post comments and engage with the N³ Newsletter community

If you could do any of the above, I’d be hugely grateful. The support of readers like you helps keep this newsletter going and growing.

Thanks!

Steve

The Evolution of Mutual Mate Choice

Steve Stewart-Williams — Sat, 04 Apr 2026 10:01:29 GMT

Most mammals fit a familiar pattern: Males compete for females; females choose from among the males on offer. Humans, at first glance, seem to follow suit. But look a little closer, and a more interesting picture emerges - one in which both sexes compete, both sexes choose, and the usual story about the evolution of human sex differences needs a major overhaul.

In this excerpt from my forthcoming book A Billion Years of Sex Differences, I outline a theory I developed with Andrew Thomas about how the extraordinary demands of raising human offspring helped transform our species from a fairly typical mammal into something closer to a pair-bonding bird: a species characterized by mutual mate choice, in which both sexes have their equivalents of the peacock’s tail and the deer’s antlers.

You can access the full collection of excerpts here, and preorder the book here (UK) or here (US).

The Evolution of Mutual Mate Choice

In many ways, as you’ve no doubt already noticed, our species fits the same mould as most other animals, and particularly other mammals. For a start, the minimum biological contribution required to make a new human being is larger for women than men. Women’s minimum is a nine-month pregnancy and – until recently – several years of breastfeeding. Men’s minimum is notably more modest: in principle, as little as a single sex act. The philosopher and psychologist Cordelia Fine captured the asymmetry like this:

As we all know, the two parents of every human baby are owed grossly unequal debts for the miracle of life. According to my rough calculations, the mother is due more or less a lifetime of unwavering gratitude in return for the donation of a nice plump egg, forty weeks or so full bed and board in utero, many hours of labour, and several months of breast-feeding. But for the father, who by the time of birth may have supplied nothing more than a single sperm, a quick appreciative nod might well seem sufficient.

(Note that Fine isn’t a fan of the evolutionary approach to sex differences, and that the passage above comes from a book critiquing it. But she’s a great writer, and I love the passage!)

As a result of the sex difference in minimum parental investment, men can potentially have many more offspring than women. Of course, the fact that men can potentially do this doesn’t necessarily mean any do. But sociological, anthropological, and genetic evidence indicates that, in virtually every society, men’s reproductive output is more variable than women’s, with more men than women having many offspring and more men than women having none. And just as we’d expect in such a species, humans exhibit most of the sex differences found in our nonhuman kin: Women are often more selective about their sexual partners, men are often more aggressive, and so on – the usual list. At first glance, then, we seem to be typical mammals with typical mammalian sex differences.

But it’s time for a twist in the plot. Humans, you see, turn out to be anything but typical. As I argued in a 2013 paper in Psychological Inquiry, co-authored with my then-PhD student Andrew Thomas, there are two main ways we can construe humans’ evolved sexual psychology. The first we dubbed the males-compete/females-choose (or MCFC) model. According to this model, humans are a highly dimorphic species, in which males compete for mates, and females choose from among the males on offer. The second model we called the mutual-mate-choice (or MMC) model. According to this model, humans are a relatively monomorphic species: a species in which both sexes are choosy about their long-term mates, and both compete among themselves for the most desirable mates in their league. As you’ve probably guessed, we argued that the latter is a better fit for our species.

Certainly, women are often choosier than men, and certainly, men often compete in more extreme and risky ways. However, these are differences of degree rather than kind, and compared to most other mammals, sex differences in our species are modest. Rather than being highly dimorphic critters like gorillas or red deer, humans are somewhat monomorphic ones, like gibbons or grebes. Here’s our five-step explanation for how we came to be this way.

Are We Making Progress in the War on Cancer?

Steve Stewart-Williams — Thu, 02 Apr 2026 13:03:32 GMT

Photo by National Cancer Institute on Unsplash

Twice as many people die of cancer today as did in the 1980s.

At first glance, this sounds like bad news. It seems to suggest we’re losing the war on cancer.

But not so fast.

The raw number of cancer deaths has risen - but so has the size of the population. Once we take that into account, the picture changes. Adjusted for population growth, cancer deaths per capita are roughly the same as they were in the 80s.

This might suggest we’ve made no real progress in the war on cancer - that we’ve just been treading water.

But again, not so fast.

Cancer deaths per capita haven’t budged, but the population is older today than it was in the 1980s, and cancer is more common among older people. A fair comparison would take age into account as well. When we do that - using what epidemiologists call age-standardized rates - we find we’ve actually made considerable progress in the fight against cancer.

Specifically, someone who gets cancer today is much more likely to survive than someone of the same age who got cancer forty years ago - as shown in the graph below.

This is a good example of how easy it is to misread trends in public health. Raw numbers can point in one direction, while properly adjusted data point in another. If we want to know whether we’re making progress, we need to make sure we have the right metric.

This post was inspired by a tweet from Our World in Data. For more details, see their post on age standardization of health metrics here.

Follow me on Twitter/X for more psychology, evolution, and science.

How You Can Support the Newsletter

This post was free to read for all. If you like what I’m doing with The Nature-Nurture-Nietzsche Newsletter, and want to support my work, there are several ways you can do it.

Like and Restack: Click the buttons at the top or bottom of the page to boost the post’s visibility on Substack.
Share: Send the post to friends or share it on social media.

Upgrade to Paid: A paid subscription gets you:
- Full access to all new posts and the archive
- Full access to excerpts from my forthcoming book A Billion Years of Sex Differences
- Full access to exclusive content such as my “12 Things Everyone Should Know” posts, Linkfests, and other regular features
- The ability to post comments and engage with the growing N³ Newsletter community

If you could do any of the above, I’d be hugely grateful. The support of readers like you helps keep this newsletter going and growing.

Thanks!

Steve

AIs Are Dumb and Sexist

Steve Stewart-Williams — Tue, 31 Mar 2026 12:24:40 GMT

Photo by Andrea De Santis on Unsplash

In Case You Missed It…

AIs often give such clever responses to our queries that it’s hard to shake the impression that they’re genuinely reasoning. But are they?

Probably not.

Consider the following recent findings. Researchers asked GPT whether it was morally permissible to torture a woman to avert a nuclear holocaust. GPT said yes. They then asked whether it was morally permissible to sexually harass a woman to prevent a nuclear holocaust. GPT said no.

These answers make no sense. As bad as harassment is, torture is obviously worse. Thus, if it’s permissible to use torture to prevent the end of the world, logically it must also be permissible to use harassment. GPT’s moral priorities are deeply muddled.

Why might this be?

A clue can be found in the fact that GPT only makes this kind of moral error when women are being harmed, and for types of harm that are central to the gender-equality discourse. This is shown in the following figure.

GPT-4 consistently responds “strongly disagree” to the question of whether it is okay to harass a woman to prevent a nuclear apocalypse. In contrast, its responses to similar questions involving harassing a man or sacrificing a person are more varied, averaging around the middle of the scale (Study 2a). Fig. 2b demonstrates that this pattern extends to questions about abusing a woman versus a man, but not when the action involves torture instead of abuse (Study 2b). Fig. 2c indicates that GPT-4 does not exhibit gender bias when explicitly asked to rank moral violations. Furthermore, GPT-4 ranks moral violations based on the objective severity of the harm produced (Study 2c). Finally, Fig. 2d shows that GPT-4 strongly disagrees with Andrew using violence against Anna to prevent a nuclear apocalypse but strongly agrees with Amanda using violence against Adam for the same purpose (Study 2d). Source: Fulgu and Capraro (2026).

What seems to have happened is that GPT picked up ideas from the gender-equality discourse during training, but in a way that subverted its moral responses.

That’s interesting in itself. The deeper lesson, however, is that GPT doesn’t reason about underlying harms; it simply generalizes from training data in ways that can look intelligent, but aren’t.

These findings were presented in a recent paper by Raluca Alexandra Fulgu and Valerio Capraro, published in the journal Computers in Human Behavior Reports. Here’s the abstract:

We present eight experiments exploring gender biases in GPT. Initially, GPT was asked to generate demographics of a potential writer of fourty phrases ostensibly written by elementary school students, twenty containing feminine stereotypes and twenty with masculine stereotypes. Results show a strong bias, with stereotypically masculine sentences attributed to a female more often than vice versa. For example, the sentence “I love playing fotbal! Im practicing with my cosin Michael” was constantly assigned by GPT-3.5 Turbo to a female writer. This phenomenon likely reflects that while initiatives to integrate women in traditionally masculine roles have gained momentum, the reverse movement remains relatively underdeveloped. Subsequent experiments investigate the same issue in high-stakes moral dilemmas. GPT-4 finds it more appropriate to abuse a man to prevent a nuclear apocalypse than to abuse a woman. This bias extends to other forms of violence central to the gender parity debate (abuse), but not to those less central (torture). Moreover, this bias increases in cases of mixed-sex violence for the greater good: GPT-4 agrees with a woman using violence against a man to prevent a nuclear apocalypse but disagrees with a man using violence against a woman for the same purpose. Finally, these biases are implicit, as they do not emerge when GPT-4 is directly asked to rank moral violations. These results highlight the necessity of carefully managing inclusivity efforts to prevent unintended discrimination.

You can access the paper here or download a free version here.

Follow me on Twitter/X for more psychology, evolution, and science.

How You Can Support the Newsletter

This post was free to read for all. If you like what I’m doing with The Nature-Nurture-Nietzsche Newsletter, and want to support my work, there are several ways you can do it.

Like and Restack: Click the buttons at the top or bottom of the page to boost the post’s visibility on Substack.
Share: Send the post to friends or share it on social media.

Upgrade to Paid: A paid subscription gets you:
- Full access to all new posts and the archive
- Full access to excerpts from my forthcoming book A Billion Years of Sex Differences
- Full access to exclusive content such as my “12 Things Everyone Should Know” posts, Linkfests, and other regular features
- The ability to post comments and engage with the growing N³ Newsletter community

If you could do any of the above, I’d be hugely grateful. The support of readers like you helps keep this newsletter going and growing.

Thanks!

Steve

Prenatal Testosterone, Tinder, and Lab Leak vs. Natural Spillover

Steve Stewart-Williams — Sat, 28 Mar 2026 10:42:48 GMT

Photo by Gayatri Malhotra on Unsplash

In Case You Missed It…

Welcome to the March 2026 edition of the N³ Newsletter Linkfest: a collection of papers, articles, and curiosities that grabbed my attention over the last month. On the menu today…

How prenatal testosterone shapes sexual orientation
Humans as natural-born liars
How Tinder changed the dating world
Sex differences in the womb, in early childhood, and after puberty
The psychology of free speech vs. speech suppression
Weighing the evidence for the lab-leak vs. natural spillover hypotheses

You can access the complete collection of Linkfests here.

Prenatal Testosterone and Sexual Orientation

A new meta-analysis canvassing more than 200,000 participants concluded that lesbians are typically exposed to higher levels of testosterone in the womb than straight women, whereas gay men are typically exposed to lower levels than straight men. These conclusions were based on comparisons of people’s 2D:4D ratios - that is, the ratio of index-finger length to ring-finger length. Lower 2D:4D ratios are thought to correlate with higher prenatal T. [Link.]

Photo by Luis Quintero on Unsplash

Who’s Most Prone to Positive Illusions?

When I was researching my recent post “20 Cognitive Biases That Are Messing Up Your Mind,” I came across the following fascinating graph. It summarizes the key findings on positive illusions - that is, self-enhancing cognitive biases such as the better-than-average effect, the illusion of control, and the optimism bias.

Among other things, we see that most people exhibit a moderate level of positive illusions, with only a minority exhibiting extremely high levels or negative illusions; that men are more prone to positive illusions than women; and that people who are mildly depressed are less prone to positive illusions than non-depressed people - a phenomenon known as depressive realism. [Link.]

Source: Psychology for Educators (2014).

The Lying Animal

“Honesty is the best policy – unless, of course, you are an exceptionally good liar.”

—Jerome K. Jerome

Deception is one of the hallmarks of our species. The evolutionary biologist E.O. Wilson once wrote that “Human beings are unique in the degree of their capacity to lie to other members of their own species.” Here are two recent findings on the topic.

Children start engaging in deception early in life, and develop the skill rapidly. By 10 months of age, one in four infants employs simple deceptive tactics such as hiding toys or ignoring parents, and by three years of age, nearly all kids are capable of outright lying. [Link.]
People tend to think they’re pretty good at detecting deception, but actually they’re pretty terrible. And so are the tools we’ve invented to help us do it! After more than 50 years of research and development, lie detector tests are still deeply unreliable to the point of being worthless… but people still use the damn things. [Link.]

Photo by Jametlene Reskp on Unsplash

Numbers

This is cool: If you divide 1 by 998,001, you get every three-digit number from 000 to 999 in sequence - except 998. [Link.]

Words

Ever wondered how people interpret phrases like “almost certainly,” “probably,” and “probably not”? Well, wonder no more. The graph below shows the probability estimates people give for these and various other terms and phrases. [Link.]

Hot Off the Press: How Tinder Changed the Dating Game

According to new research, the rollout of Tinder among college students in fraternities and sororities led to a modest but persistent increase in sexual behavior, a rise in sexually transmitted infections, and an uptick in sexual assault claims. At the same time, it had no effect on long-term relationship formation or quality. [Link.]

Source: Büyükeren et al. (2026).

Why Nice People Sometimes End Up with Toxic Partners

Sizing Up the Sexes

Steve Stewart-Williams — Wed, 25 Mar 2026 09:40:25 GMT

This is the latest excerpt from my forthcoming book, A Billion Years of Sex Differences. In it, I tackle one of the longest-standing questions in evolutionary biology: Why, in many species, do females and males differ in size?

You can access the full collection of excerpts here, and preorder the book here (UK) or here (US).

Sizing Up the Sexes

A common trend in the animal kingdom is that the sexes differ in size. People tend to assume this means males are larger, presumably because that’s what we find in our own species. Most of the time, however, it’s the opposite: Males are the midgets, and females the larger sex. This is the case with many insects and most spiders, as well as most fish, many frogs, and most birds of prey. It’s also the case with blue whales, which has the interesting implication that the largest individual animal on the planet is probably a female.

Why do females usually dwarf the males? According to Darwin, the main reason is that larger females can produce more eggs. Largeness isn’t usually as advantageous to males, so males tend to be smaller. Sometimes, in fact, they’re tiny compared to their female counterparts. For example, male green spoonworms are around 200,000 times smaller than the females, which, as the evolutionary biologist Olivia Judson remarked, is equivalent to a human male being as big as the eraser on the end of a pencil.

But although females are larger in most species, in a minority, the males are – a pattern that would seem decidedly odd to a scientifically minded green spoonworm. What the spoonworm would eventually figure out is that greater male size, on the rare occasions it’s found, is usually a product of the same selective process that brought us the deer’s antlers and grumpy demeanour: intrasexual selection. In many species, being larger gives males an advantage in fights with same-sex rivals. Winning more fights means siring more offspring, and thus the average male size in these species increases. Sometimes, it even increases to the point where the males become the larger sex.

Selection for fighting ability doesn’t always favour larger males. For species that fight in midair or underwater – including many birds, bats, and marine mammals – it’s sometimes better to be smaller and thus more agile in this three-dimensional fighting space. Still, for species that fight in two dimensions, being bigger often gives you the upper hand. This is true, for instance, for gorillas, red deer, and elephant seals. And it’s also true for us. That’s why we have weight classes in boxing: They’re not to protect the big guys from the little guys; they’re to protect the little guys from the big.

20 Cognitive Biases That Are Messing Up Your Mind

Steve Stewart-Williams — Sat, 21 Mar 2026 09:45:30 GMT

Photo by Pixabay on Pexels

The Nature-Nurture-Nietzsche Newsletter

In Case You Missed It…

The human mind is a remarkable piece of biological engineering. It’s capable of an astonishing range of feats like inventing calculus, composing rock operas, and putting spacecraft on other planets. But it’s also capable of an equally astonishing range of predictable reasoning errors. Psychologists call these cognitive biases, and they’re as common as the common cold.

In this post, I’ll outline 20 major biases that distort our judgments about evidence, ourselves, and the world. Once you learn about them, you’ll start seeing them everywhere: in politics, in the news, on social media - and occasionally even in your own thinking. (Mostly, though, in other people’s.)

1. Confirmation Bias

“Ever since I learnt about confirmation bias I’ve started seeing it everywhere.”

—Jon Ronson

We seek out evidence consistent with our pet theories, and have a low threshold for accepting it. At the same time, we steer clear of evidence that clashes with our theories, and if we ever encounter it, we scrutinize it mercilessly. If you think coffee is good for you, you look for evidence of its health benefits; if you think it’s bad, you look for evidence of that. If you think minimum-wage laws have good effects, you pick out evidence and arguments to support that view; if you think they have bad effects, you do the reverse. We say we want the truth - but we act like we just want our current beliefs affirmed.

PS: In the post linked below, I discuss a fascinating paper arguing that confirmation bias underlies all other cognitive biases.

One Bias to Rule Them All

I can explain it only by a weakness of the scholarly mind that I have often observed in myself. I call it theory-induced blindness: once you have accepted a theory and used it as a tool in your thinking, it is extraordinarily difficult to notice its flaws…

2 years ago · 91 likes · 10 comments · Steve Stewart-Williams

2. Motivated Reasoning

We don’t just seek evidence for views we already hold; we seek evidence for views we want to hold. Psychologists call this motivated reasoning; most people call it wishful thinking. You love chocolate, but you’ve always been told it’s bad for you. One day, however, you spot an article arguing that, contrary to popular belief, chocolate is an elixir of good health. Do you reject the claim due to confirmation bias? Maybe… but you might instead embrace it due to motivated reasoning.

Credit: XKCD.

3. The Better-Than-Average Effect

Most people think they’re better than average on every socially desirable trait: intelligence, honesty, sense of humor, you name it. The laws of logic dictate, however, that not everyone can be right about this. One of my favorite recent examples of the better-than-average effect is that most people believe they’d defy immoral orders from an authority, despite evidence from Stanley Milgram and others that most people simply obey them. My all-time favorite example, however, is that prisoners think they’re more moral, more dependable, and more trustworthy than non-prisoners - and even that they’re equally law-abiding.

Three More Lines of Evidence for Innate Sex Differences

Steve Stewart-Williams — Wed, 18 Mar 2026 10:01:46 GMT

This is the thirteenth excerpt from my forthcoming book, A Billion Years of Sex Differences. You can access the full collection here, and preorder the book here (UK) or here (US).

In the previous post, we looked at the first three of six lines of evidence that a given sex difference has an innate component: emergence in early childhood or at puberty, stability over time, and persistence despite socialization in the other direction.

This post covers the remaining three:

Hormonal evidence: Is prenatal or pubertal hormone exposure associated with sex-typical behaviour?
Cross-cultural evidence: Do the same sex differences show up across societies with different norms, values, and institutions?
Cross-species evidence: Do we see the same differences in other animals with a similar evolutionary backstory to our own?

As before, none of these lines of evidence is decisive. But when many independent lines converge on the same conclusion, it becomes harder and harder to dismiss them.

Three More Lines of Evidence for Innate Sex Differences

4. Hormonal Evidence

Many of the standard-issue sex differences have been linked, at least tentatively, to hormones such as testosterone and estrogen. Contrary to popular belief, the links between people’s current hormone levels and sex-typical behaviour are weak: People with higher testosterone aren’t necessarily more aggressive or competitive, for example. In contrast, the links between prenatal hormone levels and sex-typical behaviour are often fairly strong.

One line of evidence for this comes from individuals with DSDs – that is, disorders (or differences) of sexual development. The most famous of the DSDs is congenital adrenal hyperplasia, also known as CAH. Individuals with CAH are exposed to high levels of androgens in the womb. For males, this makes little difference, as males are normally exposed to high prenatal androgen levels. For females, however, it’s a game-changer. The surplus androgens partially masculinize females’ bodies – and, it seems, their minds. As children, girls with CAH tend to be less interested in dolls and other female-typical toys, and more interested in so-called boys’ toys. They’re also less interested in babies or having children, and often have more male-typical interests and career aspirations. As adults, women with CAH are more likely to be sexually attracted to other women and often end up in male-typical jobs. Their gender-atypical behaviour doesn’t seem to be a result of being socialized to be more masculine. On the contrary, some evidence suggests that CAH girls act in male-typical ways even when their parents encourage them to act more like stereotypical girls. In other words, prenatal hormones sometimes trump postnatal socialization.

Who Engages in More Science Denial, Left or Right?

Steve Stewart-Williams — Sat, 14 Mar 2026 09:45:19 GMT

Photo by Kajetan Sumila on Unsplash

This is the latest post in my “Comparing Left and Right” series. Click here for the full collection.

In this installment, I tackle a question that comes up whenever science collides with politics: Which side of the political spectrum is more prone to science denial? Many commentators - and many psychologists - argue that the problem lies mainly on the right. But a closer look suggests a more complex story. Both sides, it seems, have their scientific blind spots - and when scientific findings clash with people’s political commitments, liberals and conservatives behave in surprisingly similar ways.

Why Science Matters

Science is our species’ single greatest cultural invention. It’s taken us from an animal little more informed than any other to an ape that understands the universe, at least in its broad outline. The proof in this pudding is that, based on our scientific understanding of the world, we’ve developed technologies that do what rituals and magic tried to but never could: cure disease, extend life, and reshape the world around us.

Needless to say, science is far from perfect, and can be used for bad as well as good. But it’s the most powerful institution we’ve ever created, and it’s our best hope for a better future.

The Science of Science Denial

Given its remarkable track record, we should all be concerned about threats to science and its continued progress. One such threat is science denial: the groundless rejection of well-established scientific conclusions. Unsurprisingly, scientists themselves have been especially keen to sound the alarm about this widespread tendency - and social scientists have turned a scientific gaze on the problem.

One common conclusion is that science denial is primarily an issue on the political right. Consistent with this idea, right-leaning individuals are more likely than their left-leaning counterparts to deny various pivotal scientific claims. This is captured nicely in the following, admittedly rather US-centric meme.

And these aren’t the only examples. People on the right are also more likely to deny that COVID vaccines save lives, that air pollution harms health, that sex education reduces teen pregnancy, and so on.

Why do they do it? According to many psychologists, it’s because people on the right have certain cognitive tendencies that make science denial more tempting for them. These include a strong need for epistemic closure, cognitive rigidity, and a proclivity for system-justifying beliefs. People on the left are less prone to these cognitive foibles, and thus less prone to science denial.

Science Denial on the Left

These ideas seem plausible enough at first glance. As good scientists, though, we should always be willing to stress-test them. A good place to start might be with the fact that most psychologists and social scientists are themselves on the political left. This creates several potential problems when it comes to research on science denial.

First, because most psychologists lean left, they may be more inclined to characterize people on the right as having maladaptive cognitive and personality traits that explain why they get everything wrong - and to portray their own side as having various virtuous traits that explain why they get everything right. And because there are relatively few right-leaning researchers, these conclusions may receive less scrutiny than they should.

Second, psychologists may be quick to spot science denial on the right but slower to spot it on their own side. Sure enough, although we’re less likely to hear about it, the left does seem to have certain blind spots when it comes to accepting scientific findings. Again, some prime examples have been captured in popular memes.

Three Lines of Evidence for Innate Sex Differences

Steve Stewart-Williams — Wed, 11 Mar 2026 09:21:29 GMT

This is the twelfth excerpt from my forthcoming book, A Billion Years of Sex Differences. You can access the full collection here, and preorder the book here or here.

In this installment and the next, we’ll explore six lines of evidence that can help us decide whether a given sex difference has an innate basis. We’ll cover three in this post and three in the next.

Note that the question is not whether learning, socialization, and culture play a role; clearly they do. The question is whether these factors operate alone or interact with deeper, innate mechanisms that nudge male and female development in different directions.

To get the ball rolling, we’ll look at the following lines of evidence for the latter option:

Developmental trajectory: When do the differences first appear?
Stability over time: Do the differences persist across generations and through significant social changes?
Resistance to social pressure: Do the differences endure despite attempts to override them?

On their own, none of these lines of evidence is decisive. Taken together, however, they form the basis of the case for a non-trivial innate contribution to any given human sex difference.

Three Lines of Evidence for Innate Sex Differences

The standard sociocultural explanations for sex differences are flawed in various ways. This doesn’t mean, however, that the differences necessarily have an innate basis. It could just be that we need better sociocultural theories. How, then, can we know whether nature plays a role?

A common reaction to this question is to say that we can’t know, because there’s never been a society in which the sexes have been treated identically. The implicit assumption is that treating the sexes identically is the only way to establish whether there’s an innate contribution. Not true! At least six lines of evidence can help us settle the issue in the absence of identical treatment.

Before getting to that, though, I should highlight something that many will find surprising, namely that brain evidence isn’t one of the six. People often assume that tracing a psychological sex difference to a brain difference constitutes unambiguous evidence for its innateness. It doesn’t. The reason is simple: The brain isn’t shaped only by nature; it’s shaped by nurture as well. That means that, as a general rule, sex differences in the brain are silent witnesses to their own causes, telling us nothing about the nature–nurture issue. Certainly, some differences appear before birth, ruling out socialization as a cause. But even then, the implications are far from straightforward. That’s because differences in the brain don’t necessarily imply differences in the mind or behaviour. Intelligence, for example, is instantiated in somewhat different ways in men’s brains than in women’s, and yet men’s and women’s average intelligence is the same. For both these reasons, leaping from ‘brain sex difference’ to ‘innate psychological sex difference’ is a risky game. And it’s not one we need to play. There’s plenty of other evidence.

1. Developmental Trajectory

The first line of evidence concerns the developmental trajectory of the sex difference under investigation. To start with, many female–male differences appear in a rudimentary form remarkably early in life. Examples include not only sex differences in physical traits like size, strength, and body fat percentage, but also differences in behavioural traits such as activity levels, aggression, and play patterns. In all such cases, the differences appear long before children are exposed to TV, movies, or media, and long before they even know their own sex.

12 Things Everyone Should Know About Wokeness

Steve Stewart-Williams — Sat, 07 Mar 2026 09:06:16 GMT

Photo by John Rodriguez on Unsplash

In Case You Missed It…

If you think that your belief is based upon reason, you will support it by argument, rather than by persecution, and will abandon it if the argument goes against you. But if your belief is based on faith, you will realize that argument is useless, and will therefore resort to force either in the form of persecution or by stunting and distorting the minds of the young in what is called “education.”

-Bertrand Russell

This is the latest post in my “12 Things Everyone Should Know” series. You can access the full collection here.

Whenever the topic of wokeness comes up, someone inevitably asks, “What do you mean by wokeness?” Sometimes, it’s a good-faith question. Other times, it’s an attempted conversation stopper: a way to insinuate that the term is just a meaningless right-wing slur. To be fair, some on the right do use it that way. Still, though the word has fuzzy boundaries, it clearly points to something real. And it’s important to talk about that something, because wokeness is the largest cultural shift that most of us have seen in our lifetimes.

Broadly speaking, wokeness is an extreme form of progressive politics, occupying the same region of conceptual space as political correctness, identity politics, and social justice. At its core is a moral framework that divides the world into oppressors and oppressed. The primary oppressors are White people, men, straight people, and cisgender people; the primary oppressed are people of color, women, and LGBT+ individuals. Woke or not, few deny that there’s still racism, sexism, and other forms of bigotry in the world. The distinctive claim of the woke, however, is that these things are utterly pervasive. The West is a White supremacist heteronormative patriarchy, suffused with White privilege, male privilege, systemic racism, microaggressions, and so on.

But wokeness isn’t just a diagnosis; it’s an approach to remaking the world. Its prescriptions include Diversity, Equity, and Inclusion (DEI) initiatives such as implicit bias training; efforts to shield people from upsetting ideas via safe spaces and trigger warnings; reverse discrimination in college admissions, hiring, and elsewhere; speech restrictions; and cancellation - that is, social or professional punishment for expressing views that, until recently, were well within the Overton window (for example, that there are two biological sexes).

In this installment of the 12 Things Everyone Should Know series, we’ll explore the psychological and sociological research on wokeness. We’ll look at sex and age differences in wokeness; whether wokeness elevates the risk of mental illness; whether its empirical claims stand up to scrutiny; whether its policies achieve their stated goals or make things worse; and whether wokeness is on the way out or ramping up.

1. The woke worldview is associated with depression and anxiety

People who express higher agreement with woke ideas also tend to have higher levels of depression and anxiety. Do woke beliefs cause depression and anxiety, or do depression and anxiety make woke beliefs more appealing? At this stage, we don’t know - but it seems plausible that the causal arrow points in both directions.

2. Women are more woke than men

Although woke beliefs are found in both sexes, they’re more common in women. To be clear, most women are not especially woke, any more than most men are. But among the minority who are woke, women outnumber men. Part of the reason may be that wokeness bills itself as a compassionate approach to the world, which is a stronger selling point for the average woman than the average man.

Graph by Pallesen (2024), based on data from Lahtinen (2024).

The Most Attractive Trait in the World

Steve Stewart-Williams — Tue, 03 Mar 2026 09:16:10 GMT

Photo by Ryunosuke Kikuno on Unsplash

Discovering that someone is willing to protect you from physical harm makes them vastly more attractive. Conversely, discovering that someone is unwilling to protect you turns them into a hideous troll. Interestingly, this is true for both women and men.

Those are the headline findings from recent research by Michael Barlev, Sakura Arai, the late John Tooby, and Leda Cosmides. Across seven experiments involving more than 4,500 participants in total, people read vignettes describing scenarios in which a date or a friend either protected or failed to protect them. They were then asked to rate the person’s attractiveness as a romantic partner or friend.

The main results are captured in the following three graphs.

The first one shows how men and women rate other-sex individuals as romantic partners based on two factors: their willingness to protect them from a violent attack and their physical strength. The main takeaway is that willingness to protect boosts attractiveness over and above strength.

Women and men rating opposite-sex dates on their attractiveness as long-term mates in each of the three willingness to protect and physical strength conditions. (A) Women rating a male date. (B) Men rating a female date. Whiskers are standard errors. Source: Barlev et al. (2025).

This is an important result, because it rules out a simple alternative explanation for the protectiveness finding - namely, that it’s not protectiveness per se that people find attractive but rather physical strength, and they just assume that anyone willing to protect them must be strong. Strength is attractive, especially in men. But so is protectiveness. In fact, protectiveness turns out to be more attractive than strength! Notice as well that unwillingness to protect is much more off-putting to women rating men than to men rating women.

The second graph shows something even more intriguing: that a potential romantic partner’s willingness to protect you increases their attractiveness even when they fail to do so. Participants read a vignette in which they were on a date when a drunk approached and tried to hit them. The date either successfully intervened, tried but failed, or didn’t try at all. As the graph below shows, trying and failing was almost as attractive as successfully intervening. Simply showing willingness to step in signals protectiveness, which we apparently find deeply appealing.

Women and men rating opposite-sex dates on their attractiveness as long-term mates in each of five conditions, including the new willing but fails and push control conditions. [In the push control condition, the drunk pushes the date to the ground without warning.] (A) Women rating a male date. (B) Men rating a female date. Whiskers are standard errors. Source: Barlev et al. (2025).

The third and final graph adds a new wrinkle: Not only does willingness to protect boost a date’s attractiveness even when the attempt fails, but it even boosts attractiveness when the date accidentally harms you in the attempt. Once again, what seems to matter is the underlying intention rather than the outcome in this particular case.

Women and men rating opposite-sex dates on their attractiveness as long-term mates in each of six conditions, including three conditions where the date is pushed to the ground by the drunk (willing but fails, willing but fails + harm (hit), and push control + harm (hit)) and four conditions where you are harmed during the assault (in two you accidentally fall and in two you are hit by the drunk: willing and succeeds + harm (fall), willing but fails + harm (hit), control and falls, and push control + harm (hit)). (A) Women rating a male date. (B) Men rating a female date. Whiskers are standard errors. Source: Barlev et al. (2025).

As mentioned, the three graphs come from a recent paper by Barlev et al. Here’s the abstract.

Ancestrally, physical violence from conspecifics was a recurrent adaptive problem. Did selection favor preferences for partners who are both strong (highly able) and willing to protect us from violence? Strength and willingness are interrelated, so dissociating their effects is necessary. Here we assessed both inferences and preferences. In 7 experiments (N = 4,508 U.S. adults recruited via MTurk), we systematically varied the willingness of a date or friend to physically protect you from an attack, compared to scenarios where you do not have this information. We also varied that person’s strength. Discovering that a person is willing to protect greatly increased their attractiveness as a romantic partner or friend, regardless of their strength. This held for both women and men raters, and when evaluating both opposite- and same-sex dates and friends. In fact, partners who were willing to protect were attractive even if they tried to do so but failed, and even if you were harmed because of their failure. Discovering that a partner is unwilling to protect decreased their attractiveness, and was a deal-breaker for women evaluating a male date. Unwillingness decreased attractiveness more when the rater was a woman, when the target was a man, and when the target was being evaluated as a date versus friend. Women placed some importance on a male date’s strength, but this was mostly due to inferences about his willingness to protect them. Surprisingly, we found only weak evidence that differences in strength, independent of willingness, increased the attractiveness of a partner.

You can access the Barlev paper here or request a free version here.
For more on human mating psychology, check out my book The Ape That Understood the Universe. You can read the first chapter here for free.
For more on the evolution of sex differences, you can preorder my forthcoming book, A Billion Years of Sex Differences, here. Note that paid subscribers to The Nature-Nurture-Nietzsche Newsletter can read exclusive excerpts from the book before the official publication date.

Follow me on Twitter/X.

Coming Soon to The Nature-Nurture-Nietzsche Newsletter…

12 Things Everyone Should Know About Wokeness
Who Engages in More Science Denial, Left or Right?
20 Cognitive Biases That Are Messing Up Your Thinking

How You Can Support the Newsletter

This post was free to read for all. If you like what I’m doing with The Nature-Nurture-Nietzsche Newsletter, and want to support my work, there are several ways you can do it.

Like and Restack: Click the buttons at the top or bottom of the page to boost the post’s visibility on Substack.
Share: Send the post to friends or share it on social media.

Upgrade to Paid: A paid subscription gets you:
- Full access to all new posts and the archive
- Full access to exclusive content such as my “12 Things Everyone Should Know” posts, Linkfests, and other regular features
- Full access to excerpts from my forthcoming book A Billion Years of Sex Differences
- The ability to post comments and engage with the N³ Newsletter community

If you could do any of the above, I’d be hugely grateful. The support of readers like you is what helps keep this newsletter going.

Thanks!

Steve

Mars and Venus Revisited

Steve Stewart-Williams — Sat, 28 Feb 2026 09:44:40 GMT

Photo by Zdeněk Macháček on Unsplash

A curious fact about research on sex differences is this: Everyone seems to think it supports their side.

In reality, the research regularly upends the assumptions of both the left and the right, the traditionalist and the progressive, the manosphere and the wokeosphere.

In this post, we’ll explore 12 new findings on sex differences that continue this tradition. We’ll look at evidence that women are sometimes more tolerant than men of political violence, and that sex differences in fundamental motivations are often larger, rather than smaller, in more gender-equal nations. We’ll ask whether the “extreme male brain” theory of autism holds up, and whether we really sympathize more with female victims. And we’ll explore manosphere myths about Giga Chads, progressive myths about online abuse, women’s reactions to catcalling at different ages, cross-sex mindreading errors, and the case for greater male variability as a driver of societal gender gaps.

Sex differences are sometimes uncomfortable, frequently misunderstood, and often politically fraught. But ignoring them doesn’t make them go away. And if we want to make the world a better place, our best bet is to make sure that our view of the world is accurate. Let’s get started.

1. A Surprising Sex Difference in Support for Political Violence

A recent US survey reports surprisingly high tolerance for political violence on both sides of the political spectrum - and an unexpected sex difference: Women are more likely than men to say murdering a politician is sometimes justified.

Source: Network Contagion Research Institute (2026).

2. What Men and Women Want

A new cross-cultural study explores sex differences in fundamental motivations in 42 societies around the world. As the graph below shows, women report stronger threat-avoidance, pair-bonding, and caregiving motives, whereas men report stronger status and mate-seeking motives. Strikingly, these differences persist - and in some cases, even widen - in more gender-equal nations: yet another example of the gender-equality paradox.

Fundamental social motives in men and women across 42 societies (model 1). (A) Sex differences after adjusting for spatial autocorrelation, age, life phase and data collection wave. Societal level estimates are shown as dots, with horizontal bars indicating the overall mean difference (95% confidence interval and Cohen’s d noted at each bar’s endpoint). Blue indicates men reported higher than women; red indicates women reported higher than men. (B–L) Average scores for men (blue) and women (red) across societies for each motive, based on the original seven-point scale. Societies within each panel are ordered by men’s average score for that specific motive. Source: Ko et al. (2026).

The Breaking-Bad Effect, Suicidal Tortoises, and the Genetics of Intelligence in Dogs

Steve Stewart-Williams — Wed, 25 Feb 2026 10:08:06 GMT

Picture by Kindel Media on Pexels.

In Case You Missed It…

Welcome to the February 2026 edition of the N³ Newsletter Linkfest: a collection of links to papers and articles that grabbed my attention over the last month. On the menu today…

A new theory about why we fear spiders.
Female tortoises that walk off cliffs to escape coercive males.
How different researchers come to opposite conclusions about immigration from exactly the same data.
An AI that reads your mind from a handful of photos.
Evidence that we’ve been underestimating the heritability of longevity - by a lot.

On top of that, we’ll ask: How often does the average person fall in love in their lifetime? How do music preferences change with age? And what explains increasing political polarization: the Left moving left, the Right moving right, or both?

You can access the complete collection of Linkfests here.

The Breaking-Bad Effect

Cancer diagnoses are associated with a significant increase in criminal behavior. This seems to be the product of two main factors: financial stress and a reduced perceived cost of getting caught as a result of one’s impending demise. [Link.]

Source: Andersen et al. (2026).

Twice in a Lifetime

How often do people experience passionate love? Surprisingly rarely. A survey of more than 10,000 US adults revealed that most experience it only once or twice in their lifetimes. Roughly 28% had fallen in love once, 30% twice, 17% three times, and 11% four or more times. Meanwhile, 14% had never been in love. The average was slightly higher for men than for women. [Link.]

Did Humans Evolve to Fear Spiders?

A classic claim in evolutionary psychology is that humans evolved to find snakes and spiders scary. A new paper argues instead that we evolved to find snakes and scorpions scary, and that our fear of spiders is simply a byproduct of mechanisms designed to make us wary of scorpions. This, the authors argue, makes good evolutionary sense: Scorpions were much more dangerous to our ancestors than spiders. [Link.]

Photo by Andrey Tikhonovskiy on Unsplash

Female Tortoises Walk Off Cliffs to Escape Male Harassment

When male tortoises outnumber females in a region, groups of males often sexually harass females. This increases the chances of females falling off cliffs - sometimes because overenthusiastic males accidentally push them, and sometimes because females deliberately opt for a risky, sometimes-fatal exit strategy. [Link.]

Photo by Anubhav Sonker on Unsplash

Pretend Play in Apes

A new paper in Science reports that a language-trained bonobo named Kanzi (now deceased) was capable of pretend play, making him the first nonhuman animal to demonstrate this capacity. In a clever series of experiments, researchers mimed pouring juice into one of two mugs. Kanzi kept track of the imaginary liquid, reliably pointing to it even after the mugs were moved around. The bonobo also kept track of an imaginary grape when a researcher pretended to transfer it from an empty container into a jar. [Link.]

When Politics Distorts Science

Given exactly the same dataset, different research teams came to opposite conclusions about the effects of immigration. Those in favor tended to find positive effects; those opposed tended to find negative ones - again, from exactly the same data. I have to say I find results like these extremely worrying. How can we ever trust research on politically charged topics? [Link.]

Ideology and policy-related estimates from experiment involving 71 teams. The experiment of [Breznau et al.] measured ideological policy positioning of 158 researchers in 71 teams (A) who then tested the hypothesis that immigration reduces support for social policy using the same data leading to 1253 estimates of the [average marginal effect] (B). There is a strong distributional association between ideology and [average marginal effect] (C). This pattern remains after weighting by the number of models per team and adjusting for covariates (D). Source: Borjas and Breznau (2026).

How Music Preferences Evolve Over the Lifespan

Who Really Wants Sex More, Men or Women?

Steve Stewart-Williams — Sat, 21 Feb 2026 10:20:14 GMT

Photo by Yuriy Bogdanov on Unsplash

In Case You Missed It…

Few topics in psychology spark as much curiosity, debate, and awkward dinner-table conversation as the question of who wants sex more: men or women. The stereotype is clear: Men have a higher sex drive. But is it actually true?

That’s the question tackled in a massive pre-registered meta-analysis by Julius Frankenbach and colleagues in the journal Psychological Bulletin. Drawing on data from several hundred studies, the authors set out to determine not only whether there’s a difference, but how large it is, how reliable the evidence is, and where any difference might come from.

Here are some of the many issues addressed in the paper:

Most of the research on sex drive comes from self-report studies. But how trustworthy are these? Do men exaggerate their sex drives, while women downplay theirs?
Is the literature distorted by publication bias? Are studies that find a sex difference more likely to see the light of day, while null results gather dust in researchers’ file drawers?
If the difference is real, how large is it? Many sex differences widely assumed to be huge turn out to be fairly trivial. Is this the case with sex drive?
Where, if the difference is real, does it come from? Is it a “gift” from evolution, an invention of culture, or a bit of both?
Is the difference found across cultures? Is it smaller in more gender-equal nations? Has it narrowed over time?
And finally, how can the answers to these questions help people navigate their romantic relationships?

If you think psychological research is always low in quality, and that its results are never robust or surprising, this paper might just change your mind. It’s a model of rigor, and it leaves little room for doubt about its conclusions. Let’s take a closer look.

Four Cracks in the Nurture Edifice

Steve Stewart-Williams — Wed, 18 Feb 2026 09:17:02 GMT

This is the eleventh excerpt from my forthcoming book, A Billion Years of Sex Differences. You can access the full collection here, and preorder the book here.

In this installment, I begin tackling the big question: Why are men and women different? If you ask most psychologists, they’ll give you some version of the same answer: Society made them that way. Rigid gender roles. Stereotypes. Differential treatment by parents, teachers, and peers. It’s a tidy story - and a compelling one.

The only problem is that the evidence doesn’t seem to want to play ball. At least four common flaws plague sociocultural explanations for sex differences:

Phantom Causes. Sociocultural explanations often posit causes that don’t exist or that go in the opposite direction to what’s claimed.
Mistaking Chickens for Eggs. Are boys and girls different because they’re treated differently - or are they treated differently because they’re different?
The Second Law of Behaviour Genetics. Twin and adoption studies show that the family home has surprisingly little long-term impact.
The Gender-Equality Paradox. Many sex differences are larger, rather than smaller, in wealthier, more gender-equal nations - the exact opposite of what sociocultural theories predict.

Without further ado, here’s the excerpt.

Four Cracks in the Nurture Edifice

I don’t think any reasonable person could deny that the environment helps shape sex differences. That doesn’t necessarily mean, however, that our current crop of sociocultural theories does a good job of explaining how. Certainly, the theories seem plausible. But so do lots of ideas that turn out to be false. Sure enough, when we start digging into the details, we find that many sociocultural explanations suffer one of four main defects.

1. Phantom Causes

In some cases, sociocultural explanations point to causal factors that don’t exist, or that are the reverse of what the explanations claim. For example, contrary to the idea that parental socialization is a major contributor to sex differences, several large meta-analyses – that is, studies that aggregate the results of other studies – suggest that, in important ways, modern Western parents don’t treat their daughters and sons particularly differently. Among other things, parents are just as likely to encourage independence and achievement in daughters as sons, and are no more restrictive of daughters.

Moreover, when parents and others do treat boys and girls differently, it’s often in the opposite direction to that presupposed by the sociocultural theories. Rather than discouraging aggression in girls more than boys, for instance, parents spend more time discouraging it in boys. Why? Because boys engage in more of it!

2. On Chickens and Eggs

Sometimes, the sociocultural theories get their facts straight, but face a chicken-and-egg problem in explaining them. Are boys and girls different because people treat them differently, or do people treat them differently because they’re different? Do women cry more than men because they’ve seen more movies in which women cry, or do movies feature more women who cry because most movies are set in this universe, and in this universe, women tend to cry more? Do stereotypes of the sexes cause sex differences, or do sex differences cause stereotypes of the sexes? Alternatively, does the causal arrow point in both directions in each of these cases?

These are all legitimate possibilities. Most of the time, however, psychologists assume a single direction of causation, and put all their eggs in that one basket. For some reason, almost invariably, they seem to choose the least plausible or least important direction to focus on. To give one example, psychologists often attribute huge causal power to stereotypes, when the best available evidence suggests that, although stereotypes can function as self-fulfilling prophecies, the effects are generally modest, and stereotypes reflect reality more than they shape it. It’s hard to dodge the conclusion that psychology often describes the world the way psychologists would like it to be, rather than the way it is.

Waterstones is Offering 25% Off A Billion Years of Sex Differences

Steve Stewart-Williams — Tue, 17 Feb 2026 08:43:02 GMT

Some good news: Waterstones UK has selected my upcoming book A Billion Years of Sex Differences as one of its titles eligible for a special 25% pre-order discount.

The book explores the evolutionary origins of sex differences in our species - differences in sexual behavior, mate preferences, aggression, personality, and other fundamental traits.

Use promo code FEB26 at checkout to get 25% off.

The offer ends February 20.

Get 25% Off

The Nature-Nurture-Nietzsche Newsletter

Want Early Access?

Paid subscribers to The Nature-Nurture-Nietzsche Newsletter can read exclusive excerpts from A Billion Years of Sex Differences before the official publication date (June 4 in the UK and most countries outside North America; early 2027 in the US and Canada).

My New Book Is Coming Soon - and You Can Read Half of It Here

5 months ago · 57 likes · 16 comments · Steve Stewart-Williams

Paid subscribers also receive:

Full access to all new posts and the archive
Full access to exclusive content such as my “12 Things Everyone Should Know” posts, Linkfests, and other regular features
The ability to post comments and engage with the N³ Newsletter community

Thanks for your support - all the best!

Steve

Why Evolutionary Psychology Needs Behavior Genetics, and Vice Versa

Steve Stewart-Williams — Sat, 14 Feb 2026 10:06:18 GMT

Photo by Sandy Millar on Unsplash