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Sex and intelligence: 3.6 extra points

J. Philippe Rushton, a well-known psychologist from University of Western Ontario, has done a work that would otherwise be nothing else than a routine exercise. He extracted the g-factor - "pure intelligence" - from the SAT results of 100,000 American teenagers. One of his conclusions was that

See also The result applies to young people who are 17-18 years old, after the effect of girls' getting mature earlier starts to disappear.

Their article with Douglas N. Jackson

appears in the September issue of Elsevier's journal Intelligence. But because the topic is politically loaded, the work is not just a pile of boring numbers. Rushton had to produce dozens of disclaimers what the results don't mean and how unhappy he is to have obtained these results, and all this nonsense. And still, he is not safe.

Lawrence Summers had to resign as the president of Harvard University. The main reason was that in January 2005, he offered his working hypothesis why women lag in science and engineering during a conference whose official goal was to study why women lag in science and engineering.

The same Harvard University will host Mohammad Khatami on Sunday, less then 20 hours before the fifth anniversary of the 9/11 attacks. Right now, all of us are very proud of the academic freedoms and open-mindedness. Hundreds of people will admire the great thinker from Iran who will offer his impressive and thoughtful theories that Israel is a piece of dirt on the map where the shameful U.S. foreign policy is being created. Daniel Wolfson called the Harvard's combined attitude to Summers and Khatami "Crimson hypocrisy" in the Boston Herald. Stronger words could be more appropriate.

Back to the SAT tests.

A year ago or so, Helmuth Nyborg, a leading Danish psychologist, published an article

in a peer-reviewed journal called Personality and Individual Differences. The Inquisition was ready.

Recall that many Danish products are very advanced and the Danish Inquisition has a rather sophisticated structure, too. In 2001, Bjorn Lomborg published a book "The Skeptical Environmentalist" in which he demonstrated that the effects of climate change wouldn't be too important and they would probably be beneficial anyway. The Inquisition's activities entered full gear. A bizarre branch of the Inquisition called

started to cling mud on Lomborg. It took almost a full year until a ministry of the Danish government decided, in December 2003, that the bigots in DCSD didn't handle the investigation properly and their conclusions were invalid.

With this precedent in mind, you can guess what happened to Helmuth Nyborg if his peer-reviewed, accepted paper argued for an IQ difference of 8 points (or 3.8 points, depending on certain subtleties, or 4.55, after a certain set of errors was caught) between men and women. Svend Hylleberg, the dean of social sciences at Aarhus University, asked Nyborg to vacate his position in 2006.

Of course, the international science community was extremely upset because of this witch-hunt. J. Philippe Rushton, Linda Gottfredson, and lots of econometrists were defending Nyborg as much as they could. But still, you know that a rational discussion with bigots is an extremely difficult enterprise. Nowadays, sex and intelligence is a more sensitive topic for them than heliocentrism. Many of these empty skulls have been high-profile people. For example, David Peterson, a former "progressive" Ontario premier and a huge opponent of free trade, had said that he would have fired Rushton immediately if he could have. ;-)

The higher male variance of the IQ distribution has been a well-established piece of science for quite some time. The difference between the averages seems to be between 3 and 4 points according to many recent studies by Rushton, Nyborg, as well as Richard Lynn from 1999. Of course, this difference depends on the details how the quantities are defined and measured.

But unfortunately, the main topic that the researchers can freely focus on is not the question whether the difference is 3 or 4 and what it depends on. The main topic is how can they ever justify the incredible heresy to suggest that the difference could be anything else than zero.

Well, the explanation is due to Murray Gell-Mann, it is called the totalitarian principle, and it applies to all of science. Everything that can occur - everything that is not prohibited by an exact symmetry of the physical system - will occur. There is clearly no exact symmetry between men and women, and all conceivable differences and correlations will indeed occur. There is certainly no good open Yes/No question in the research of these differences. The real questions are quantitative: how much, what is the cause, what does it mean, and how rational policies should be influenced by these insights.

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reader Eric Crampton said...

Suppose that men and women have equal mean IQ but men have higher variance. A greater proportion of men won't hit the threshold necessary even for bothering to take the SAT -- there's no way they're going to university. If you have two distributions of equal mean, then cut off the lower tails of both, and the tails are fatter in one than the other, you're automatically gonna affect the mean of those who are left. The evidence described is entirely consistent with equal average population IQ; it's just that the bottom tail of the male distribution isn't taking the SAT. No?

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