In 2008, using populationwide surveys of general intelligence among eleven-year-olds in Scotland, a team of researchers based at the University of Edinburgh confirmed that males did show more variability in their test results. These differences aren’t extreme as some in the past have suggested they are, they note, but they are substantial. At the same time, the authors point out that the biggest effect is seen at the bottom end of the scale. Those with the very lowest intelligence scores tend to be male.
