Monday, April 26, 2010

Are men smarter than women?

According to the New York Times:
In a closely watched case, a sharply divided federal appeals court on Monday ruled 6-5 that a sex discrimination lawsuit against Wal-Mart could proceed as a class action for more than a million women. The suit is the biggest employment discrimination case in the nation’s history.
The evidence for discrimination that the plaintiffs offer is that while 65 percent of Walmart's hourly employees are women, only one-third of its managers are.

Let's pack it in and go home--I, for one, am convinced that Walmart places hatred of women above its desire to make a profit.

The Gods of Human Biodiversity must have been guiding my path today: I was in the middle of reading a research study on the male advantage in IQ when I heard about the lawsuit. 

For years I've assumed that men and women have the same average general intelligence. Why have I assumed this?  Because King Arthur Jensen told me so. In the g Factor. Now, I'm not so sure. 

In the journal Personality and Individual Differences, Danish researcher Helmuth Nyborg reviewed studies examining sex differences, and of the several methodological criteria set by Nyborg, only one study was adequate. Many of the criteria are technical, but the most compelling to me is that results depend a lot on the mix of subtests, some which favor males and some which favor females. The way around the problem is to maximize the number of subtests, which makes sense since general mental ability is supposed to penetrate a broad array of cognitive tasks.

The study that meets all of his requirements is by Colom et al. (2002) which gives a male advantage of 3.6 points. He then goes on to describe the results of his study based on two Danish samples--one of children and one of adults--where 20 subtests were given. (That's a lot). The male advantage in g for the kids was 3.15. When the adult sample was added to increase statistical power, the male advantage rose to 6.90 points.

Nyborg was then able to closely predict the observed sex gap in general intelligence with the sex difference in brain size (men have bigger brains--one-third of a standard deviation larger). The bigger brains give men 15 percent more neurons.  

Now a few IQ points doesn't seem like a big deal, but that gets magnified at the high end. Based on his Danish data, for every woman with an IQ of 145 or higher, you will get eight men.

We shouldn't be the least bit surprised to see men dominate the higher ranks of a large organization. And that's not even counting higher natural levels of ambition, competitiveness, and dominance.  

Makes me wonder about the sex of the plaintiff's lawyers.     

UPDATE: Dennis Mangan explains how biological differences explain lower pay for women here.


  1. I have always felt that it is not reasonable to assume that men and women would have identical intelligence unless proven otherwise; because Men's and women's brains are of different size, have different compositions, and developed in a very different hormonal 'culture medium'.

    They were also subjected to significantly different evolutionary selection pressures.

    If, after all these differences, male and female brains converged on an identical degree of general intelligence, it would be something of a miracle.

    'No difference' is therefore not a plausible null hypothesis.

  2. I skimmed the Wal-Mart article in the Wall Street Journal and I think it said Wal-Mart does not plan to settle. This would seem to me to imply they believe they can still win the case, but I don't know enough about the legal system to be sure.

  3. dearieme3:15 PM

    I don't think that this argument holds water. Consider:
    "the mix of subtests, some which favor males and some which favor females." Quite, which is why the early IQ researchers weighted their tests so that the two sexes got the same average score for IQ. Having thus fixed the mean, they discovered the much larger standard deviation for men. So far so sensible. Then your quotation continues:
    "The way around the problem is to maximize the number of subtests, which makes sense since general mental ability is supposed to penetrate a broad array of cognitive tasks." That seems to make no sense: how can you "maximize"? There is no upper bound. Set 100. Set 1000. Set 10000.
    The essential problem is that men and women have, on average, intrinsically different mental strenghts, so reducing them to a single "IQ" score is necessarily arbitrary. If you want to fuss about, say, the paucity of women in jobs involving maths, cite the scores on the maths-related tests, don't try to stretch the concept of IQ to do a task for which it is a bit too crude.

  4. Men get promoted into management because of personality traits, not intelligence. There is little reliable mean difference in intelligence between the sexes, the difference is in the variance, which produces the male advantage at the right tail to which you refer.

    This advantage does not get very strong until about 130+ IQ, probably too high to affect the typical Wal-mart manager selection process. It is likely that there are only 10-20% more males above the Wal-Mart "cut score", which would result in a gender imbalance of no more than 55% males, 45% females. The 65%/35% ratio would require a male advantage of 1.86 to 1, which is huge.

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