The Test Scores That Kept Rising and Then Stopped

Throughout the twentieth century, raw scores on intelligence tests rose in many countries by roughly three points a decade, a pattern named for the political scientist James Flynn. Test makers responded by restandardising their tests every few years, so that the average always sits at one hundred, which hides the climb from anyone who reads only the published scores.

Then researchers using Norwegian military records reported that scores for men born after the mid 1970s had begun to fall. Because the decline appeared between brothers in the same families, the authors concluded that genes and migration could not explain it, and that something in the environment had changed. Some commentators point to schooling or media, but no explanation has won general agreement, and no one has shown that the earlier rise reflected a rise in underlying ability rather than a change in the skills the tests happen to reward.