Sex Differences in IQ

Conventional wisdom overturned

The conventional wisdom about sex differences in IQ is that males and females have the same average IQ. The conventional wisdom also stipulates that males are more variable than females, meaning that there are more mentally deficient and gifted males than females.

Presented here is information from two good papers on sex differences in IQ that disagree yet end up having the same conclusion with regard to the high extreme of IQs. Additionally, data from Mensa Canada is given that agrees with both those papers on that point.

Before continuing, it might be prudent to tackle one of the first objections that will be raised to a finding that the sexes are not equal in terms of IQ: that IQ tests are biased. Test bias is an intricate subject, and if you are interested in the details, the book Bias in Mental Testing by Arthur R. Jensen is suggested. (He started out believing that IQ tests were biased and through careful research ended up concluding that they generally were not).

Let it suffice to point out the analogy of height differences: Men are taller on average than women. If one does not like the situation, one cannot seriously accuse the height-measuring device of being biased. Many people have been influenced by anti-IQ reporting in the media, and politically correct writings by authors such as Stephen J. Gould to think that if IQ tests show an inequality it is obvious evidence that they are biased. There are ways of measuring test bias and merely showing that there is a difference between groups is not enough.

WISC-R

The paper that supports the conventional wisdom is Jensen, A. R., & Reynolds, C. R. (1983). It finds that females have a 101.41 mean IQ with a 13.55 standard deviation versus males that have a 103.08 mean IQ with a 14.54 standard deviation. You may want to read the IQ Basics page first if you are unfamiliar with IQ and standard deviations. By just looking at those figures, it seems to corroborate the conventional wisdom that has been known for decades: the average IQs are about the same and males are a bit more variable. However, if the summary data is used to generate a graph, a different picture emerges: