Are men smarter than women?

Question

I recently stumbled across the following article: Sorry, men ARE more brainy than women (and more stupid too!) It's a simple scientific fact, says one of Britain's top dons, in which the author claims:

1. That men are on average smarter than women:

one of the main reasons why there are not more female science professors or chief executives or Cabinet ministers is that, on average, men are more intelligent than women.

Boys and girls may start out with the same IQ but by 16 or so boys are starting to inch ahead. The ever-growing success of girls at GCSE, A-level and now at university would seem to refute this - but the blame lies with our exam system, with its emphasis on coursework, which rewards diligence more than it does intelligence.

The undeniable, easily measurable fact remains that, by the time both sexes reach 21, men, on average, score five IQ points higher than women.

2. That very-high-IQ men are much more common-place than very-high-IQ women:

For not only is the average man more intelligent than the average woman but also a clear and rather startling imbalance emerges between the sexes at the high levels of intelligence that the most demanding jobs require.

For instance, at the near-genius level (an IQ of 145), brilliant men outnumber brilliant women by 8 to one. That's statistics, not sexism.

In this context, Professor Greenfield's indignation that only one in ten science professors is female doesn't seem all that bad. It also goes some way to explaining why, in almost 110 years of Nobel Prize history, only two women have ever won the Prize for physics, only four have won the Prize for chemistry and why no women at all have ever won the coveted Fields Medal for mathematics in eight decades of trying.

This perplexed me, as I thought women and men were intellectually on par with each other. Is the article right or wrong: about the relative average intelligences of adults, and the ratios of exceptional intelligences?

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The article makes other claims as well, related to personality, for example:

Consequently, ambitious, high-achieving men typically work harder, compete more aggressively and become totally immersed in their careers, while even the most high-achieving women will often admit to finding themselves distracted by their genetically preconditioned aptitude for nurture and support.

To keep this question focussed, please ignore such claims about personality, and about what may cause gender imbalance in the job markets, and focus only on the claims about "intelligence" as made above.

Answer 1

The title of the article is "Sorry, men ARE more brainy than women (and more stupid too!) It's a simple scientific fact, says one of Britain's top dons" - note the bolded part.

The article makes two independent claims, only one of which is relevant to the social/political topic being discussed (lack of women in top positions):

1. There are more males with extremely high IQ compared to female (which is counterbalanced with having a lot more men with extremely low IQ compared to women).

   In scientific terms, the IQ distribution has fatter tails in males.

   There are astonishingly few studies (due to political sensitivities of the topic) either confirming or denying that, but the main one cited is usually the Scottish early 20th century survey, which is exceptional in that it looked at a vast majority of children of the studied age group.

   

   Note that there are virtually identical amount of men and women with "normal" IQ (85-120 IQ) - the differences are +/- 2% one way or the other.

   But on a gifted level (typically considered to be 130-160) there are 15-20% differences at low end. The graph doesn't even show true genius levels (160+) but extrapolating the trend, it's likely that the differences are even higher (I've seen mentions of 1:8 ratios but couldn't find a reliable source on short order).

2. The second one is that on average, male IQ is higher than female.

   Frankly, I'm somewhat skeptical of this claim myself, but don't have time to dig out studies (as the topic under discussion is imbalance of women in top positions that typically involve 130+ IQ, I see the claim as irrelevant even if true).

Answer 2

Short answer: If you measure IQs, taller people tend to show higher numbers, and men are taller in average. A man and a woman of the same size would show a slight difference in favour of the female. If measuring intelligence as brain components, men show slightly higher numbers and have a better short-term memory.

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Adam Hampshire from the University of Western Ontario has very recently conducted a research with 100,000 participants of different age, gender and geographical locations, criticising the use of IQ tests as a measure of intelligence. They run cognitive tests that analysed the memory, reasoning, attention and planning abilities, and reinforced them with MRI scanning.

For a century or more many people have thought that we can distinguish between people, or indeed populations, based on the idea of general intelligence which is often talked about in terms of a single number: IQ. We have shown here that’s just wrong. Results from the study found that given a broader range of cognitive tasks, the differences in ability relate to at least three components of intelligence – short-term memory, reasoning and verbal aptitude. These three components combined create an intelligence, or "cognitive profile".

In other words, there is no single measure of intelligence. The components interact with one another but are handled by three distinct nerve “circuits” in the brain.

I wanted to mention this because IQ has been used as a measuring tool since the 1900s. They were created by French psychologist Alfred Binet, but Binet himself did not believe that his psychometric instruments could be used to measure a single, permanent and inborn level of intelligence (Kamin, 1995).

Works like the one cited on this answer have actually been critisised by Satoshi Kanazawa and Diane J. Reyniers in 2009.

The orthodoxy in intelligence research for the second half of the 20th century had been that men and women had the same average intelligence, but men had greater variance in their distribution than women. Most geniuses were men, and most imbeciles were men, they said, while most women were in the normal range. This conclusion, however, was manufactured out of political expediency. Not wanting to discover, or a priori denying, any sex differences in intelligence, psychometricians simply deleted from the standardized IQ tests any item on which the performance of men and women differed.

Kanazawa and Reyniers ventured another hypothesis. They started with something that had been stated before: that height is positively correlated with 'intelligence' (sources), taller people on average are 'more intelligent' than shorter people. And men in every human population are taller than women. They analysed a large representative American sample (20.745 from the National Longitudinal Study of Adolescent Health) and discovered that:

Once height (measured in inches) is controlled, women have significantly higher IQs than men. Net of height, women score 2.14 points higher on the PPVT. In contrast, each inch in height is worth more than half an IQ point (0.56). Further controlling for health, physical attractiveness, age, race, education, and earnings does not alter this conclusion. Height has exactly the same effect on intelligence for men and women: Each inch in height increases the IQ by about .4 point.

Because American men on average are 5 inches taller than American women (5'10" vs. 5'5"), this translates into 2.80 IQ points (overcoming the 2.14-point advantage of women). According to this study, when height is not controlled, men show higher IQs in average.

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These are still just abstractions for what we want to define as intelligence (IQ and g, Hampshire's ratio). Kanazawa's work offers a plausible explanation to why IQ tests show higher numbers for men, but I think it's Hampshire's research that shows a more flexible approach to the subject. Intelligence has environmental modifiers:

_{Source: Fractionating Human Intelligence}

Age was by far the most significant predictor of performance, with the mean scores of individuals in their sixties 1.7 SD below those in their early twenties.

However, the games you play, if you are an anxious person or if you smoke, all modify your final g number, or supposed intelligence.

And here comes what I think is a possible answer to this question:

While the differences between male and female participants’ mean (0.1 SD), verbal (0.03), and reasoning scores (0.03) were negligible, males showed a small advantage over females on the STM component score (0.2 SD).

Are men smarter than women?

If you measure IQs, taller people tend to show higher numbers, and men are taller. According to this, taller men are (generally, very broadly) 'smarter' than shorter men and shorter women. In average, a man and a woman of the same size would show a slight difference in favour of the female.

If measuring intelligence as brain components, men show slightly higher numbers and have a better short-term memory.

This is the latest study using 'modern' technology such as MRI scanners. The brain is still the most complex structure we possess, so I doubt any of this will remain carved in stone.

Answer 3

The accepted answer doesn't really answer the question (are men smarter than women), but a different question (did Scottish boys in 1932 perform better on an IQ test than girls).

The conclusion that is drawn is disputed by newer research. Researchers who think that men have a higher IQ argue that this discrepancy doesn't happen until 15 (although that fact is obviously disputed by researchers who do not think that there is a sex difference above age 15).

I don't have a definitive answer to the question, but I will try to give an overview over existing studies on the topic.

Studies arguing that men are smarter than women

Richard Lynn

The main proponent of the idea that men are smarter than women is Richard Lynn, whose work on intelligence has been severely criticized as biased, racist, and disregarding scientific objectivity.

In 1998 Lynn looked at sex differences in Scotland:

In a Scottish standardisation sample of the Wechsler Adult Intelligence Scale-Revised, men have a mean IQ of 105.09 and women of 100.00. The higher average mean obtained by men is consistent with four other standardisation samples of the WAIS and WAIS-R._{Lynn, 1998. Sex differences in intelligence: data from a Scottish standardisation of the WAIS-R}

An article from 1999 looked at sex differences in Estonia:

1201 applicants for entry to the University of Tartu were given tests of verbal, reasoning and spatial abilities and of scholastic knowledge. Males scored significantly higher than females on all four tests and on the g factor. The male advantage is estimated at 6.6 IQ points._{Allik, Must & Lynn, 1999. Sex differences in general intelligence among high school graduates: Some results from Estonia}

A study from 2002 looked at differences in development:

The general trend shows that girls do better at the younger ages and their performance declines relative to boys among older age groups, which supports the developmental theory. The sex difference for the DAT as a whole for 18 year olds is a 4.3 IQ advantage for boys, very close to the advantage that can be predicted from their larger brain size (4.4 IQ points). _{Lynn & Colom, 2003. Testing the developmental theory of sex differences in intelligence on 12–18 year olds}

A study from 2003 looked at data from Hong Kong:

The results are that males obtained a higher mean score than females of 1.6 raw score points, equivalent to an advantage of 3.2 or 4.1 IQ points, according to two alternative methods of calculation. _{Lynn & Tse-Chan, 2003. Sex differences on the progressive matrices: some data from Hong Kong.}

A study from 2004 looking at data from New Zealand:

Sex differences on the WISC-R were examined in a sample of 897 New Zealand children studied at ages 8 and 9 years. Boys scored significantly higher than girls on the subtests of information, vocabulary, block design and object assembly, while girls scored significantly higher on coding. Boys obtained slightly but not significantly higher scores on the verbal, performance and full scale IQs. _{Lynn, Fergusson & Horwood, 2004. Sex differences on the WISC-R in New Zealand}

Data from 2005 from Mauritius:

Sex differences on the WISC-R (Wechsler Intelligence Scale for Children-Revised) are examined in a sample of 1258 11 year olds in Mauritius. Boys obtained a significantly higher Full Scale IQ by 5.8 IQ points. Boys obtained a higher Performance IQ by 6.5 IQ points and a higher Verbal IQ by 1.0 IQ points._{Lynn et al, 2005. Sex differences on the WISC-R in Mauritius}

In 2004, Lynn and Irwing did a meta-analysis:

A meta-analysis is presented of 57 studies of sex differences in general population samples on the Standard and Advanced Progressive Matrices (SPM and APM, respectively). Results showed that there is no difference among children aged 6–14 years, but that males obtain higher means from the age of 15 through to old age. Among adults, the male advantage is 0.33 d equivalent to 5 IQ points. _{Irwing & Lynn, 2004. Sex differences on the progressive matrices: A meta-analysis}

In 2005, Lynn and Irwing did a meta-analysis of various studies. Their conclusion is that there is not a greater variability in men, but that men are smarter on average:

A meta-analysis is presented of 22 studies of sex differences in university students of means and variances on the Progressive Matrices. The results disconfirm the frequent assertion that there is no sex difference in the mean but that males have greater variability. To the contrary, the results showed that males obtained a higher mean than females by between .22d and .33d, the equivalent of 3.3 and 5.0 IQ conventional points, respectively. _{Irwing & Lynn, 2005. Sex differences in means and variability on the progressive matrices in university students: A meta-analysis}

The methodology they used has been criticized by Blinkhorn in Nature, especially for excluding a study from Mexico. Lynn and Irwing rejected the criticism.

Other

A study by Nyborg from 2003 finds a sex difference in intelligence and tries to explain why other studies don't:

The present study addressed this paradox by testing four hypotheses: (1) Inadequate analyses explain why researchers get inconsistent results, (2) The proper method will identify a male g lead, (3) The larger male brain “explains” the male g lead, (4) The higher male g average and wider distribution transform into an exponentially increased male–female ratio at the high end of the g distribution, and this largely explains male dominance in society. All four hypotheses obtained support_{Nyborg, 2003. Sex-related differences in general intelligence g, brain size, and social status}

A study by Jackson and Rushton finds differences:

In this study we found that 17- to 18-year old males averaged 3.63 IQ points higher than did their female counterparts on the 1991 Scholastic Assessment Test (SAT)._{Jackson & Rushton, 2005. Males have greater g: Sex differences in general mental ability from 100,000 17- to 18-year-olds on the Scholastic Assessment Test}

Studies arguing that there is no (or negligible) sex difference in intelligence

A study by Colom et al from 2000:

Cognitive batteries were applied in the present study to independent samples totaling 10,475 adult subjects (4,256 females and 6,219 males). The scores were factor analyzed by sex to obtain separate g factors. [...] The results suggest a negligible sex difference in g._{Colom et al, 2000. Negligible Sex Differences in General Intelligence}

A study by Flynn and Rossi-Case from 2010:

Raven’s Progressive Matrices data of high quality from five advanced nations show that females matched males both below and above the age of 14. This counts against hypotheses that genetic factors cause general intelligence differences between the genders. _{Flynn & Rossi-Case, 2010. Modern women match men on Raven’s Progressive Matrices}

A study by Savage-McGlynn from 2011 disputing the Developmental Theory of Sex developed by Lynn (the idea that men develop slower, but have a higher intelligence after the age of 15):

Using a nationally representative sample of children, multiple-group confirmatory factor analyses have been used to assess mean differences in younger (7–14 years) and older (15–18 years) groups. No significant differences were found in mean performance or score variance, failing to provide evidence for a Developmental Theory of Sex Differences in general intelligence._{Savage-McGlyn, 2011. Sex differences in intelligence in younger and older participants of the Raven’s Standard Progressive Matr}

A study by Camarata and Woodcock finds:

There was a high degree of concordance across tests and no sex difference was observed in overall estimates of general intellectual ability (GIA) on the WJ III._{Camarata & Woodcock, 2006. Sex differences in processing speed: Developmental effects in males and females}

Studies finding that there is a sex difference in favor of women

A study by Keth et al disputes the Developmental Theory of Sex:

The higher-order, latent g factor showed inconsistent differences for children, small, non-significant differences favoring females for adolescents, and fairly consistent statistically significant differences favoring females in adulthood. Findings are inconsistent with developmental theory that suggests males should show an advantage on g in adulthood. _{Keith et al, 2008. Sex differences in latent cognitive abilities ages 6 to 59: Evidence from the Woodcock–Johnson III tests of cognitive abilities}

Studies finding higher variance among men

There are studies that suggest that there is no difference in the mean, but that there is a greater variance among men. For example:

Males have only a marginal advantage in mean levels of g (less than 7% of a standard deviation) from the ASVAB and AFQT, but substantially greater variance. Among the top 2% AFQT scores, there were almost twice as many males as females._{Irwing et al, 2006. Brother–sister differences in the g factor in intelligence: Analysis of full, opposite-sex siblings from the NLSY1979}

Conclusion

This may not be satisfactory, but there is no definite answer as intelligence is a complex topic. Wikipedia provides a good overview though:

Differences in intelligence have long been a topic of debate among researchers and scholars. With the advent of the concept of g or general intelligence, many researchers demonstrated no significant sex differences in g factor or general intelligence[1][2][3][4][5][6] while others have argued for greater intelligence for males.[7][8][9][10][11][12][13] The split view between these researchers depended on the methodology[1] and tests they used for their claims.[14] One study did find some advantage for women in later life,[15] while another found that male advantages on some cognitive tests are minimized when controlling for socioeconomic factors.[16]

Answer 4

That men are on average smarter than women

Wikipedia cites a study by the author which shows there is a difference:

In 1994, Lynn concluded in a meta-analysis that an IQ difference of roughly 4 points does appear from age 16 and onwards, but detection of this had been complicated by the faster rate of maturation of girls up to that point, which compensates for the IQ difference. This reassessment of male-female IQ has been bolstered with meta-analyses with Paul Irwing in 2004[46] and 2005[47] which found a difference of 4.6 to 5 IQ points [5].They saw no evidence that this is due primarily to the male advantage in spatial visualization, and concluded that some research previously presented as showing that there are no sex differences actually demonstrates the opposite. A further study of 1,258 11-year-olds in Mauritius derived a difference of more than 6 IQ points.[48]

Wikipedia also references a critique of that study:

However, last week's publication of Blinkhorn's critique in Nature represents a major change in attitudes to their claims. He points to a number of 'serious flaws' in the approach taken by Lynn and Irwing. For a start, he accuses them of carefully selecting those IQ studies that they allowed in their meta-analysis.

In particular, he says they chose to ignore a massive study, carried out in Mexico, which showed there was very little difference in the IQs of men and women. 'They say it is "an outlier" in data terms --in other words, it was a statistical freak,' Blinkhorn said.

'It was nothing of the kind. It was just plain inconvenient. Had it been included, as it should have been, it would have removed a huge chunk of the differences they claim to have observed.'

In addition, Blinkhorn said the pair were ignoring a vast body of work that had found no differences. 'Psychologists often carry out studies that find no differences between men's and women's IQs but don't publish them for the simple reason that finding nothing seems uninteresting. But you have to take these studies into account as well as those studies that do find differences. But Lynn and Irwing did not. That also skewed their results.'

Blinkhorn also accuses the pair of adopting a variety of statistical manoeuvres that he describes, in his paper, as being 'flawed and suspect'.

Last week Irwing defended the study and accused Blinkhorn of 'attacking the men, not the science'. The study they had done 'also has to be seen in context of our other work which has shown significant sex differences in IQ. Nor is it true that we played about with our data.'

For his part, Blinkhorn is unrepentant. 'Sex differences in average IQ, if they exist at all, are too small to be interesting,' he states in Nature

It is a stark, unequivocal statement - although it will certainly not be the last word in a debate that seems likely to dog psychology for years to come.

The Wikipedia article titled Sex differences in human psychology starts by saying,

Most IQ tests are constructed so that there are no differences between the average (mean) scores of females and males.[1] Areas where differences in mean scores have been found include verbal and mathematical ability.[1]

Its section on IQ mentions several studies which show at least that professor that Lynn is not the only person to report a difference in the mean IQ:

Several meta-studies by Richard Lynn between 1994 and 2005 found mean IQ of men exceeding that of women by a range of 3–5 points.[40][41][42][43] Lynn's findings were debated in a series of articles for Nature.[44][45] Jackson and Rushton found males aged 17–18 years had average of 3.63 IQ points in excess of their female equivalents.[46] A 2005 study by Helmuth Nyborg found an average advantage for males of 3.8 IQ points.[47] One study concluded that after controlling for sociodemographic and health variables, "gender differences tended to disappear on tests for which there was a male advantage and to magnify on tests for which there was a female advantage."[48] A study from 2007 found a 2-4 IQ point advantage for females in later life.[49] One study investigated the differences in IQ between the sexes in relation to age, finding that girls do better at younger ages but that their performance declines relative to boys with age.[50] Colom et al. (2002) found 3.16 higher IQ points for males but no difference on the general intelligence factor (g) and therefore explained the differences as due to non-g factors such as specific group factors and test specificity.[38] A study conducted by Jim Flynn and Lilia Rossi-Case (2011) found that men and women achieved roughly equal IQ scores on Raven's Progressive Matrices after reviewing recent standardization samples in five modernized nations.[51] Irwing (2012) found a 3 point IQ advantage for males in g from subjects aged 16–89 in the United States.[52]

My personal opinion (or 'take-away') on this subject is that a difference of that magnitude is too small to be noticeable in real life (or "too small to be interesting" as is stated above).

That very-high-IQ men are much more common-place than very-high-IQ women

Ibid has some support for that theory:

Some studies have identified the degree of IQ variance as a difference between males and females. Males tend to show greater variability on many traits including tests of cognitive abilities,[54][55] though this may differ between countries.[56][57][58][59] A 2005 study by Ian Deary, Paul Irwing, Geoff Der, and Timothy Bates, focusing on the ASVAB showed a significantly higher variance in male scores, resulting in more than twice as many men as women scoring in the top 2%.

And:

Both Feingold (1992b) and Hedges and Nowell (1995) have reported that, despite average sex differences being small and relatively stable over time, test score variances of males were generally larger than those of females. Feingold found that males were more variable than females on tests of quantitative reasoning, spatial visualisation, spelling, and general knowledge. […] Hedges and Nowell go one step further and demonstrate that, with the exception of performance on tests of reading comprehension, perceptual speed, and associative memory, more males than females were observed among high-scoring individuals.

These studies support the theory that "high-IQ men are more common-place than high-IQ women": for example, "more than twice as many men as women scoring in the top 2%".

I'm not aware of scientific support for the more extreme version of that theory (i.e. 8-to-1 disparity at IQ 145 and above). In the article referenced in the OP, professor Lynn writes,

In recent years, the forces of political correctness have made the reporting of this sort of statistic virtually impossible.

Yet as a psychologist who has dedicated his career to the study of intelligence - and, in particular, to how it differs between the sexes - I can tell you that in my academic circles these IQ figures are barely disputed.

I don't find that argument convincing, because:

• If he has numbers to support his theory, can he really not publish them (except as indirect allegations in the Daily Mail)?
• The alleged consensus among "my academic circles" doesn't convince me, because it's easy to imagine that "his circles" are a self-selecting subset of people who don't disagree with him.