The stability of individual differences in mental ability from childhood to old age: Follow-up of the 1932 Scottish mental survey

All Scottish children born in 1921 and attending school on June 1, 1932 (N = 87,498) undertook a validated test of psychometric intelligence, The Moray House Test. We followed up 101 of these people at age 77 and re-administered the same mental ability test. Concurrent validity data are provided for the Moray House Test at age 11 (n = 1,000) and age 77 years (n = 97). The correlation between Moray House Test scores at age 11 and age 77 was 0.63, which adjusted to 0.73 when corrected for attenuation of ability range within the re-tested sample. This, the longest follow-up study of psychometric intelligence reported to date, shows that mental ability differences show substantial stability from childhood to late life.