Gee, dudes are smarter

A study published in the September 2006 issue of the journal Intelligence analyzed 145 items from the Scholastic Assessment Test (SAT) in 100,000 17- to 18-year-olds and found a male IQ advantage of 3.63 points.

It also found that the g factor–the general factor of mental ability underlay both the SAT Verbal (SAT-V) and the SAT Mathematics (SAT-M) scales with the congruence between these components greater than 0.90, and that it was the g factor that predicted student grades better than the traditionally used SAT-V and SAT-M scales.

The male and the female g factors were congruent in excess of .99, and they favored males to an equivalent of 3.63 IQ points.

The male-female differences were present at every socioeconomic level, and across several ethnic groups.

The average male advantage was found “throughout the entire distribution of scores, in every level of family income, for every level of fathers’ and of mothers’ education, and for each and every one of seven ethnic groups,” said J. Philippe Rushton, professor of psychology at the University of Western Ontario, one of the authors of the study.

The paper’s results dovetail with those from several other recently published studies showing that men–surprisingly–have a 4- to 5- IQ point advantage over women by late adolescence and early adulthood. Before that age the two sexes are equal in general intelligence.

As such, the findings overturn a 100 year consensus that men and women average the same in general mental ability.

Because girls mature faster than boys, the sex difference is masked during the school years. Since almost all the data showing an absence of sex differences were gathered on school children, this might explain why the sex difference was missed for so long.

For decades, however, psychologists have accepted that men and women differ in their test “profiles,” with males averaging higher on tests of “spatial ability” and females higher on tests of “verbal ability.” These differences were assumed to average out.

The authors of the study, psychologists Douglas N. Jackson and J. Philippe Rushton at the University of Western Ontario, conducted the study because two recent sets of observations had raised anew the question of sex differences in general intelligence.

The first was that the general factor of mental ability–g–was found to permeate all tests to a greater or lesser extent. Thus, a “spatial” test may be relatively high on g (mental rotation) or low (perceptual speed), a “verbal” test may be relatively high (reasoning) or low (fluency), as may a “memory” test be high (repeating a series in reverse order) or low (repeating a series in presented order).

More than any other factor, the test’s g loading best determines a test’s power to predict academic achievement, creativity, career potential, and job performance. Hence, the question of sex differences became formulated more precisely as: “Are there sex differences on the g factor?”

Another set of observations concerned the sex difference found in brain size and the relation between brain size and cognitive ability. Studies published in 1992 at the University of Western Ontario by zoologist C. Davison Ankney, and also by psychologist Rushton, showed men average a 100-gram advantage over women in brain weight (and volume).

A 1997 study in Denmark documented that men have 15% more neurons than women (22.8 versus 19.3 billion).

Over two-dozen Magnetic Resonance Imaging studies have confirmed a brain-size/IQ correlation of about 0.40. So, if males average a larger brain, shouldn’t they also average a higher IQ score?

British psychologist Richard Lynn at the University of Ulster in Northern Ireland, and Paul Irwing at the University of Manchester found that adult men consistently average 4 to 5 IQ points higher than adult women in a series of recent large-scale studies using a number of intelligence tests in various countries. (Irwing & Lynn’s most recent paper appeared in Nature on July 6, 2006.)

Other researchers too have found a male advantage in general mental ability, including Prof. Helmuth Nyborg at the University of Aarhus in Denmark, who earlier this year was disciplined by his university for talking to the media about his “politically incorrect” conclusions.

Prof. Rushton agreed that “these are unpopular conclusions.” He said, “only more data can determine the true nature of sex differences in cognitive ability. However, people should not be made to feel afraid to study controversial issues.”

Prof. Rushton accepted that sex differences in general mental ability could help explain the “glass ceiling” phenomenon.

But he also noted the paradox that although men may have higher IQ scores, women do increasingly well in school exams.

It will be very hard to argue that selection bias caused the sex difference in this data set, the authors wrote. “That would require the assumption that there are hypothetical respondents who, if tested, would provide a compensating female-male advantage in g that would counterbalance the findings. They would have to be found at every level of SAT performance, in every level of family income, for every level of fathers’ and of mothers’ education, and for every ethnic group examined.”

From Charles Darwin Research Institute

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5 thoughts on “Gee, dudes are smarter”

  1. An average of 3.63 points (assumedly on the 1600 point scale) is not enough to get the boys into better schools. I toasted most of my male classmates on the SATs, especially math, and on science AP exams.

    I do think there might be a “nurture” factor in that in the past, girls would stereotypically get less help from parents to get good scores. On the other hand, my parents did not help me at all with school or tests.

  2. More girls take the SAT, unless there are thousands upon thousands of really bright girls out there who aren’t taking it (way more than the number of bright boys who don’t), more dim girls than dim boys take the test. So girls get lower scores in the aggregate.

  3. The researcher’s suggestion that an average advantage of 4 to 5 points might explain the “glass ceiling” shows an intense bias that probably taints the study. That’s simply not enough difference to make a difference. Nor are the SAT results themselves predictive of anything beyond first-year performance in college. Plus, considering the colleges with competitive admissions where SATs factor highly, it turns out that what colleges a student applies to correlates with later success in life strongly, while which of these colleges they are admitted to and attend had no correlation at all. So, to the degree these institutions weight for SAT scores, they haven’t in fact succeeded in selecting the most promising students; although the self-selection in who chose to apply has already done most of that job for them, allowing even random choice to produce decent results.

    Also, the whole hypothesis of “g” is highly disputed. See Howard Gardner’s books for the details of that.

  4. I would be interested to see what the gender
    distribution is for enrollment in SAT test
    prep courses. These courses make a significant
    difference in student performance/scores on the
    SAT. Perhaps there are more boys taking these
    prep courses and are doing better on the SAT?
    Competition for university placement is getting
    tougher for boys – with more female students
    enrolled and completing their degrees:


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