According to "The Bell Curve," some groups like East Asians score a little higher than Caucasians on IQ measures, while African-Americans have exhibited slightly lower scores. The authors suggested that these differences reflect real racial characteristics and call for changes in public policies. An American Psychological Association Task Force countered that such an overgeneralization was inappropriate and asserted that ethnic diversity on IQ tests reflected more complex patterns that shift over time.
Women and men differ on specific abilities more than on overall IQ. Females excel on a number of verbal ability measures and men outperform on some visual/spacial forms of intelligence, according to a 1996 article in "American Psychologist." Men, however, seem more likely than women to score in both the high and the low ranges of general IQ tests.
James Flynn documented a cultural difference in IQ that also factors into the controversy. Since the 1950s, each subsequent generation's intelligence scores have increased. This difference is consistent across a diverse group of nearly all countries in the world.