On the Data-Ideas dimension, there was virtually no sex difference

Thursday, February 20th, 2020

Psychologist John Holland devised his theory of vocational choice in 1959. It posited six clusters of orientations. He did this with no regard to sex differences, but — as Charles Murray points out in Human Diversity: The Biology of Gender, Race, and Class — there are huge differences in where men and women land on some of those orientations, on average:

The authors assembled a database from 81 samples that amounted to 243,670 men and 259,518 women. On average, women’s vocational interests tilted toward occupations involving work with or understanding of other people; men’s vocational interests tilted toward working with things.

The biggest tilts involved the Realistic orientation — a male preference — with an effect size of –0.84, and the Social orientation — a female preference — with an effect size of +0.68.

People vs. Things and Ideas vs. Data

On the Data-Ideas dimension, there was virtually no sex difference.

On the People-Things dimension, the effect size was +0.93, meaning that women were on the People end and men were on the Things end of the dimension — a large effect size by any standard.

Does owning a car hurt your health?

Thursday, February 20th, 2020

Does owning a car hurt your health? To really answer that, you’d need a randomized trial:

But who’s going to assign long-term car ownership on the basis of a coin flip?

The city of Beijing, it turns out. Because of mounting congestion, Beijing has limited the number of new car permits it issues to 240,000 a year since 2011. Those permits are issued in a monthly lottery with more than 50 losers for every winner – and that, as researchers from the University of California Berkeley, Renmin University in China and the Beijing Transport Institute recently reported in the British Medical Journal, provides an elegant natural experiment on the health effects of car ownership.

Led by Berkeley economist Michael Anderson, the researchers followed 180 permit winners and 757 losers for roughly five years, and looked for differences caused by the acquisition of a car.

“The randomization of the lottery is what gives us confidence,” Anderson explained in a statement. “We know that the winners should be comparable to the losers on all attributes other than car ownership.”

Not surprisingly, the winners took 2.9 fewer rides a week on Beijing’s dense public-transit network, representing a 45-per-cent drop in usage. They also spent 24.2 fewer minutes each day day walking or biking than the non-winners, a 54-per-cent drop.

You’d expect these behaviour changes to have health impacts. Over all, the winners gained an average of just more than two kilograms, a difference that was not statistically significant. But the effects were more obvious when looking only at winners aged 50 or older: They gained an average of 10.3 kilograms, a statistically significant and worrisome increase.

Even gifted women who are attracted to STEM gravitate toward the life sciences

Tuesday, February 18th, 2020

Men and women have slightly different “cognitive toolboxes,” Charles Murray notes (in Human Diversity: The Biology of Gender, Race, and Class), but they also have different interests, with women more interested in people and men more interested in things. For instance, men aligned with the following:

  • “The prospect of receiving criticism from others does not inhibit me from expressing my thoughts.”
  • A merit-based pay system
  • Having a full-time career
  • Inventing or creating something that will have an impact
  • A salary that is well above the average person’s
  • believe that society should invest in my ideas because they are more important than those of other people in my discipline.”
  • Being able to take risks on my job (–0.41)
  • Working with things (e.g., computers, tools, machines) as part of my job
  • “The possibility of discomforting others does not deter me from stating the facts.”
  • Having lots of money

And women aligned with the following:

  • Having a part-time career for a limited time period
  • Having a part-time career entirely
  • Working no more than 40 hours in a week
  • Having strong friendships
  • Flexibility in my work schedule
  • Community service
  • Having time to socialize
  • Giving back to the community

The men and women surveyed weren’t typical though:

The results I just presented came from members of SMPY’s Cohort 2, born in 1964–67, who at age 13 had tested in the top 0.5 percent of overall intellectual ability: the top 1 in 200.


The SMPY women were about twice as likely to take STEM majors as the general population of female undergraduates, but this was true of the men also, and so the male-female ratio in STEM degrees among the SMPY sample (1.6) was fractionally higher than the ratio in the general undergraduate population (1.5).


Even gifted women who are attracted to STEM gravitate toward the life sciences (People-oriented), not math and the physical sciences (Things-oriented). It was not a subtle tendency. Proportionally, males outnumbered females by almost two to one on the Things-oriented sciences, and females outnumbered males by almost two to one on the People-oriented sciences.

The test yielded 26 male-female comparisons

Monday, February 17th, 2020

Charles Murray continues to explain sex differences in cognitive skills (in Human Diversity: The Biology of Gender, Race, and Class):

The most famous cognitive measure is the IQ test. The tests are designed to minimize sex differences, but minor sex differences in test scores do exist, and they have usually, though not always, favored males.


Girls outscored boys in reading in every single PISA country, with effect sizes that ranged from a low of +0.08 in Peru to a remarkable high of +0.83 in Jordan.


“Sex differences in mental rotation and line angle judgment performance were universally present across nations, with men’s mean scores always exceeding women’s mean scores.”


In all, the test yielded 26 male-female comparisons. Twelve of them amounted to an absolute effect size of less than 0.1. Women outscored men on six of the seven measures of accuracy with an effect size greater than 0.1, and they outscored men on four of the seven measures of speed with an effect size greater than 0.1.

  • Females had more accurate memory for items involving words and people.
  • On IQ-like items, women did better on the verbal ones; men did better on the spatial ones.
  • On the three subtests measuring social cognition, females were both more accurate and faster than males on all of them.
  • On the subtest measuring motor speed, males were faster than females.

Even when men do well in social cognition tasks, they are not using the cognitive tools most naturally suited to that purpose

Sunday, February 16th, 2020

On average males have substantially better visuospatial skills than females — as evidenced by the Piaget water-level test and the bicycle-drawing test — while women have better social cognition. Bright men can compensate, as Charles Murray explains (in Human Diversity: The Biology of Gender, Race, and Class, based on Diane Halpern’s Sex Differences in Cognitive Abilities):

Males are rarely good at both systemizing and empathizing. In contrast, these skill sets are largely independent in women.


The same study found evidence that men apply systemizing skills to empathizing tasks. Put another way, even when men do well in social cognition tasks, they are not using the cognitive tools most naturally suited to that purpose.

Your two best strategies are to be really healthy and really rich

Sunday, February 16th, 2020

If you hope to live a long time, Alex Hutchinson (Endure) reminds us, your two best strategies are to be really healthy and really rich:

That’s the conventional wisdom and the statistics seem to back it up. But a surprising new study that links the longevity of Olympic athletes to their socioeconomic status offers a more nuanced picture of why elite athletes tend to outlive the rest of us. It’s not just about muscles and money — it’s also about the stress of competition, not only in sport, but in life.

Adriaan Kalwij, an economist at Utrecht University in the Netherlands, combed through the records of every Dutch athlete who competed in the Summer and Winter Games between 1896 and 1964, excluding more recent years because most of those athletes are still alive. Using their birth dates, death dates and stated occupation, he was able to explore how socioeconomic status (SES) influenced their longevity.

The results, published in PLOS One in December, confirmed that the 934 Olympians outlived their age-matched Dutch peers by a few years, as other studies of elite athletes have previously found. They also found that the influence of SES has steadily increased over the past century.

In the oldest cohort of athletes, born between 1852 and 1899, SES had no significant effect on longevity. In a sense, Kalwij says, this is what you might expect of Olympians: “excellent innate health could make them ‘immune’ to a SES-lifespan gradient.”

But in the next cohort of athletes, born between 1900 and 1919, a gradient emerges. Those classed as low SES, such as unskilled labourers, lived on average five years less than medium (teachers, office workers) and high (lawyers, doctors) SES athletes.

And in the most recent cohort, born between 1920 and 1947, an even wider gap emerges: High SES athletes lived five years longer than medium SES athletes, who in turn lived six years longer than low SES athletes — a stunning difference of 11 years between the top and bottom group, despite their healthy youth.

What’s most surprising about this trend is that it’s going the wrong way. You’d expect that the strengthening of social programs such as universal health care and state pensions over the past half-century would have reduced the health penalty incurred by poverty. Instead, Kalwij’s results join a large body of data across numerous countries, including Canada, suggesting that the influence of social class on lifespan has been growing since the 1950s.

While there are numerous factors that could contribute to an SES-health gradient, including access to health care and behaviours such as smoking and drinking, Kalwij believes that psychological stress may play a role.

I think we need to keep in mind that socio-economic status changed dramatically over the 20th Century, from inherited wealth and titles to inherited traits.

97 males and 7 females got perfect scores

Friday, February 14th, 2020

Average men and women have similar verbal and math abilities Charles Murray notes (in Human Diversity: The Biology of Gender, Race, and Class, leaning on Diane Halpern’s Sex Differences in Cognitive Abilities), but not as similar at the extremes:

On tests with nationally representative samples, females can be expected to consistently outperform males on a variety of verbal tasks, with a small advantage in reading and a more substantial advantage in writing.


To the question, “Is the typical male better at math than the typical female?” the answer is close to settled: “If yes, not enough to be noticeable,” with an open possibility that a small gap will close altogether.


“Sex differences in mathematics become progressively larger as the sample becomes more selective and the type of math skill becomes more advanced,” writes Halpern, and herein lies a major issue in the study of cognitive sex differences.


The last 60 years have seen major reductions in the male advantage at the extreme high end for 7th graders. For those in the top two percentiles, a ratio of about 2.0 in 1960 appears to have disappeared. For those in the top percentile, a male ratio of about 7.0 has fallen to around 1.5. At the most stratospheric level, the top 1 percent of the top 1 percent, a male advantage that was measured at about 13 to 1 in the 1970s and the early 1980s has fallen to less than 3 to 1.


In short, what was once thought to be an overwhelming male advantage at high levels of math achievement has been greatly reduced during the last six decades.


The male-female ratios in the top percentiles of the AMC12 are substantial and they grow larger at the 98th and especially the 99th percentile. In the table, I counted perfect scores of 150 as being in the 99th percentile. When they are broken out separately, it turns out that from 2009 to 2018, 97 males and 7 females got perfect scores: a ratio of 13.9.

Memory comes in many forms

Thursday, February 13th, 2020

Memory comes in many forms — long-term and short-term, “autobiographical,” “episodic,” and “semantic,” among others — Charles Murray notes (in Human Diversity: The Biology of Gender, Race, and Class), and females have an advantage in some of them (as Diane Halpern notes in Sex Differences in Cognitive Abilities):

  • Females tend to be better than males at remembering faces and names.
  • Females tend to be better than males at recognizing facial emotions.
  • Females tend to be better at remembering the minutiae of an event (labeled peripheral detail), while males tend to be better at remembering the core events (labeled gist).
  • Females tend to remember speech they have heard better than males, particularly when it relates to emotionally laden events in their past.
  • Females tend to retain memories from earlier childhood better than males do.
  • Females tend to have better short-term memory than males (e.g., given a list of single-digit numbers, they remember longer lists than males do).
  • Females tend to have better verbal working memory (e.g., remembering a list of numbers while answering questions about an unrelated topic).
  • Females tend to have better memory for locations of objects (e.g., remembering where the car keys were left).
  • Males tend to have better visuospatial memory (e.g., navigating on the basis of a combination of landscape features).

Females have an advantage on certain perceptual-motor tasks

Wednesday, February 12th, 2020

In Human Diversity: The Biology of Gender, Race, and Class, Charles Murray continues his list of specific skills and aptitudes that each sex performs better, taken from Diane Halpern’s Sex Differences in Cognitive Abilities, with a look at perceptual-motor tasks:

  • Females have an advantage on certain perceptual-motor tasks. On digit-symbol coding, for example, where each symbol corresponds to a number (e.g., “substitute 2 for #”), women code faster than men do.
  • Females have an even larger advantage in a variety of fine motor skills involving hand-eye coordination.
  • In tests of motor skills, it sometimes happens that men are faster but women are more accurate.
  • Men have a substantial advantage in many large motor skills, but few of them have much to do with cognition. The major exception is males’ pronounced advantage on tasks that involve throwing objects accurately at stationary or moving targets, because that accuracy is highly dependent on visuospatial processing in the brain.

Throwing like a girl is definitely a thing.

The story is mostly one of small female advantages

Monday, February 10th, 2020

In Human Diversity: The Biology of Gender, Race, and Class, Charles Murray relies on Diane Halpern’s fourth edition of Sex Differences in Cognitive Abilities (2012) for his list of specific skills and aptitudes that each sex performs better. He starts with sensory perception:

When it comes to the five senses — taste, touch, smell, sound, vision — the story is mostly one of small female advantages.

  • Females tend to be better than males at detecting pure tones.
  • Adult females tend to have more sensitive hearing for high frequencies than males.
  • Females tend to have better auditory perception of binaural beats and otoacoustic emissions.
  • Females tend to detect faint smells better than males.
  • Females tend to identify smells more accurately than males.
  • Males under 40 tend to detect small movements in their visual field better than females.
  • Age-related loss of vision tends to occur about ten years earlier for females than for males.
  • Males are many times more likely to be color-blind than females (the ratio varies by ethnic group).
  • The balance of evidence indicates that females are more accurate than males in recognizing the basic tastes (sweet, sour, salty, bitter), though some studies find no difference.
  • Females tend to be better than males at perceiving fine surface details by touch. This holds true for blind people as well as sighted ones.

Women are also more sensitive to pain and to disgust.

The only question is how long it will take

Sunday, February 9th, 2020

In Human Diversity: The Biology of Gender, Race, and Class, Charles Murray discusses the McCrae study, which looks at differences in personality traits between men and women in 50 different countries, rich and poor, from around the world:

The great cultural and economic disparities across these countries make it difficult to see how all of them could produce uniform socialization of girls to be more warm, altruistic, sympathetic, sociable, and artistically sensitive than men.

I use gender egality in preference to gender equality to signify not just progress toward diminishing sex differences but also institutional, legal, and social changes intended to put men and women on an equal footing.

The question at hand is whether sex differences in personality are smaller in countries that have made the most progress.

The theories of socialization and of social roles that I summarized in chapter 1 necessarily expect that the answer is yes. If sex differences in personality are artificial, diminishing the causes of artificial differences must eventually lead to smaller differences.

The only question is how long it will take.

This brings us to a counterintuitive finding that seems to cut across a variety of sex differences: Many sex differences in cognitive repertoires are wider rather than smaller in countries with greater gender egality. Personality traits offers the first example.


On average, women preferred altruism, trust, and positive reciprocity more than men and were more averse to negative reciprocity than men. In the two nonsocial preferences, men preferred risk-taking and waiting for a larger reward more than women.


Five different studies, based on different measures of personality and national gender egality, analyzing data from dozens of countries, all found the same pattern: overall consistency in male-female differences in personality, but larger differences in the most advanced countries


Perhaps we’re looking at a general phenomenon that goes far beyond personality traits. For example, the Schmitt study points out, sexual dimorphism in height increases with a country’s wealth. So too with sexual dimorphism in blood pressure. So too with competitiveness in sports — as opportunities and incentives increase for women to compete in sports, sex differences in performance increase as well. So too with differences between advantaged and disadvantaged groups in health and education when new opportunities are made available to all. Two years after the Schmitt study made these points, another study led by Richard Lippa found that sexual dimorphism in visuospatial abilities also increased with gender equality.

Another surprise from the Schmitt study was its finding that men do most of the changing, in both the physiological and personality traits. When sexual dimorphism in height increases, for example, it is primarily due to greater height among males. In the case of personality, the Schmitt study found that the wider sex gap in emotional stability in advanced countries is not the result of women becoming less emotionally stable, but of men self-reporting higher levels of emotional stability, and also lower levels of agreeableness and conscientiousness, than men in less advanced countries.

End­stopped neurons respond both to motion and to the terminations of a stimulus’ edges

Sunday, February 9th, 2020

Gwern recently cited a paper, Attention and awareness in stage magic: turning tricks into research, that describes the neural basis of spoon bending and the dancing bar illusion:

Spoon bending. In this illusion the magician bends a spoon, apparently by using the power of the mind. In one part of the trick, the magician holds the spoon horizontally and shakes it up and down. This shows that the neck of the spoon has apparently become flexible. The apparent rubberiness of the spoon is an example of the Dancing Bar (or Rubber Tree) illusion, in which an oscillating bar (or rubber tree) seems to bend when it is bounced rapidly. The neural basis of this illusion lies in the fact that end­stopped neurons (that is, neurons that respond both to motion and to the terminations of a stimulus’ edges, such as corners or the ends of lines) in the primary visual cortex (area V1) and the middle temporal visual area (area MT, also known as area V5) respond differently from non­end­stopped neurons to oscillating stimuli. This differential response results in an apparent spatial mislocalization between the ends of a stimulus and its centre, making a solid object look like it flexes in the middle.

On many important personality traits, the differences between men and women are quite small

Saturday, February 8th, 2020

After discussing proto-feminist Mary Astell in Human Diversity: The Biology of Gender, Race, and Class, Charles Murray discusses the differences in personality traits between men and women:

It is appropriate to begin by emphasizing that on many important personality traits, the differences between men and women are quite small. These trivial differences apply to many characteristics that are sometimes ascribed to men (e.g., “assertive or forceful in expression,” “self-reliant, solitary, resourceful”) and ones that are sometimes ascribed to women (e.g., “open to the inner world of imagination,” “lively, animated, spontaneous”).


Among the traits on which men and women differ, some of the largest effect sizes are consistent with the higher prevalence of depression among women.


Some of the substantively significant sex differences correspond to traditional stereotypes about feminine sensibility. In the FFM inventory, women were more appreciative of art and beauty than were men (d = +0.34 and +0.33 for the Costa and Kajonius studies respectively), were more open to inner feelings and emotions (d = +0.28 and +0.64), were more modest in playing down their achievements (d = +0.38 and +0.45), and were more reactive, affected by feelings, and easily upset (d = +0.53). In the 16PF inventory, several stereotypical characteristics were combined into one factor, “sensitive, aesthetic, sentimental,” with a whopping d of +2.29.


A person who is warm, sympathetic, accommodating, altruistic, and sociable amounts to the stereotype of a human being, male or female, who is more attuned to people than things. Women are more likely to have that profile than are men.


People who are somewhat to the other side of each trait in the table are reserved, utilitarian, unsentimental, dispassionate, and solitary — which amounts to the stereotype of a human being, male or female, who is more attracted to things, broadly defined, than to people. Men are more likely to have that profile than are women.

Can you draw a bicycle?

Thursday, February 6th, 2020

We overestimate our ability to explain how things work. Cognitive psychologist Rebecca Lawson at the University of Liverpool measured how well people understand how everyday objects work using the bicycle:

I have given the test to over 200 students and parents coming to Open Days at the University. Over 96% had learnt to cycle as children with a further 1.5% learning as adults and less than 3% never having learned. Also 52% of this group owned a bicycle. Sadly, the figures on actual cycling were low, with just 1% cycling most days, 4% cycling around once a week and 9% cycling about once a month. The vast majority either never cycle (52%) or rarely do so (33%). Nevertheless, even for these non-cyclists, bicycles are a common sight. Secondly, if Rozenblit and Keil are correct, people should greatly over-estimate their understanding of how bicycles work because bicycle parts are visible and they seem to be simple, mechanical devices.

Draw a Bicycle Figure 1

I first asked people to draw a bicycle and I then asked them to select which of four alternatives were correct for the frame, the pedals and the chain, see Figure 1. I used the multiple choice test to check that errors that people made were not just due to problems with drawing or in my judgement of the accuracy of their drawings, see Figure 2.

Draw a Bicycle Figure 2

I looked at three types of errors which would severely impair the functioning of a bicycle (see Figure 3 for examples of all three):

1. drawing the frame joining the front and back wheels (making steering impossible)

2. not placing the pedals between the wheels and inside the chain (the pedals were sometimes drawn attached to the front wheel, the back wheel or dangling off the cross-bar)

3. not putting the chain around the pedals and the back wheel (these errors were almost all because people drew the chain looping around both the front and the back wheel of the bicycle)

Draw a Bicycle Figure 3

It seems that many people have virtually no understanding of how bicycles work. This is despite bicycles being highly familiar and most people having learnt how to ride one. Most people know that turning the pedals drives one or both of the bicycle wheels forward, but they probably understand little more than this.


One last thing: unexpected sex effects. One finding that I was not looking for jumped out from the data. There were huge sex differences with females making many more errors than males.


Thus, at least for frame and chain errors, females make around twice as many errors as males. It could be argued that this is still a matter of experience. It is likely that boys cycle more than girls so many males who currently rarely cycle may have, over their lifetime, seen and used more bicycles than females. However the sex difference is even more extreme for those who claim to cycle around once a month, once a week or most days.


Not only do male non-cyclists make fewer errors than female non-cyclists, they also make fewer errors than female cyclists; whilst male cyclists make almost no errors.

This won’t deter critics from saying it’s all pseudoscience

Wednesday, February 5th, 2020

Despite his experience co-writing The Bell Curve, Charles Murray went ahead with Human Diversity: The Biology of Gender, Race, and Class:

I’m also at a point in my career when I’m immune to many of the penalties that a younger scholar would risk.

He thought he was careful with The Bell Curve, and it wasn’t enough — if only because no one read the book before attacking it. He has tried being careful again:

Almost all of the findings I report are ones that have broad acceptance within their disciplines. When a finding is still tentative, I label it as such. I know this won’t deter critics from saying it’s all pseudoscience, but I hope the experts will be yawning with boredom because they know all this already.