the 21st century has witnessed a resurgence of research on gender differences in variability, with most of the emphasis on humans. the results vary based on the type of problem, but some recent studies have found that the variability hypothesis is true for parts of iq tests, with more men falling at the extremes of the distribution. in general, most researchers have failed to find greater variability in either sex in any area that is consistent across cultures and not confounded by social factors.