I prepared the chart above for an article AEI's Christina Sommers is working on.  The graph displays the IQ test results from the article "Population Sex Differences in IQ at Age 11: The Scottish Mental Survey 1932," based on "80,000+ children—almost everyone born in Scotland in 1921—tested at age 11 in 1932."

Main conclusion of the article: "There were no significant mean differences in cognitive test scores between boys and girls, but there was a highly significant difference in their standard deviations ( P < .001). Boys were over-represented at the low and high extremes of cognitive ability."

As the chart shows, boys outnumbered girls both for: a) IQ scores below 95 and b) IQ scores above 115.  Further, the share of boys increased going out towards both ends of the distribution, so that boys represented 57.7% of the highest IQ scores of 140 (136 boys for every 100 girls) and 58.6% of the lowest IQ scores of 60 (142 boys for every 100 girls). 

The authors speculate that their findings might "explain such cognitive outcomes as the slight excess of men achieving first class university degrees, and the excess of males with learning difficulties.

This evidence also supports what former Harvard President Larry Summers said (and for which he was fired):

"It does appear that on many, many different human attributes- height, weight, propensity for criminality, overall IQ, mathematical ability, scientific ability - there is relatively clear evidence that whatever the difference in means - which can be debated - there is a difference in the standard deviation, and variability of a male and a female population."