Sex differences in variability: Evidence from math and reading assessment in Italy

A meta-analytical approach was used to test the greater male variability hypothesis using the mathematics and reading performance of more than 26 million Italian children across second, fifth, and eighth-grade. In keeping with the hypothesis, boys were more variable than girls in mathematics performance especially in more developed geographic regions with larger sex differences. However, there was no clear pattern for sex differences in variability in reading performance, although there was a trend for boys to be more variable in regions with larger sex differences, favoring girls. These results provide a robust test of the greater male variability hypothesis and suggest that it is not a ubiquitous phenomenon but rather varies across traits.