Some kids do bloom late, intellectually. Others start out fine but then, inexplicably, fall behind. But according to new studies, for the most part people’s mental abilities relative to others change very little from childhood through adulthood. Relative intelligence seems as resistant to change as relative nose sizes.
One of the more striking findings comes from the longest follow-up study ever conducted in this field. On June 1, 1932, Scotland had all children born in 1921 and attending school — 87,498 11-year-olds — take a 75-question test on analogies, reading, arithmetic and the like. The goal was to determine the distribution of intellectual ability. In 1998, scientists at the Universities of Edinburgh and Aberdeen tracked down 101 of those students, then 77 years old, and administered the same test.
The correlation between scores 66 years apart was a striking .73. (A correlation of 1 would mean no change in rankings; a correlation of .73 is very high.) There is “remarkable stability in individual differences in human intelligence” from childhood to old age, the scientists concluded in a 2000 paper.