The Impact of Childhood Intelligence on Later Life: Following Up the Scottish Mental Surveys of 1932 and 1947.

TLDR

The Scottish Mental Surveys of 1932 and 1947 gathered IQ‑type scores for nearly all children born in 1921 and 1936 who attended school on the survey dates. This study used those data to assess how intelligence differences persist across the life span, what drives cognitive change from childhood to old age, and how childhood IQ influences later survival and health. Researchers tested surviving participants and linked their survey scores to public and health records to track cognitive trajectories and health outcomes. The analysis revealed that IQ scores remain stable from age 11 to 80, identified sex differences in cognitive aging, supported the dedifferentiation hypothesis, and showed that higher childhood IQ reduces all‑cause and specific mortality, morbidity, and frailty in old age.

Abstract

The Scottish Mental Surveys of 1932 and 1947 collected valid IQ-type test scores for almost everyone born in 1921 and 1936 and attending school on June 1, 1932 (N=89,498) and June 4, 1947 (N=70,805). These surveys are described. This research, using the surveys' data, examined (a) the stability of intelligence differences across the life span, (b) the determinants of cognitive change from childhood to old age, and (c) the impact of childhood intelligence on survival and health in old age. Surviving participants of the Scottish Mental Surveys were tested, and the surveys' data were linked with public and health records. Novel findings on the stability of IQ scores from age 11 to age 80; sex differences in cognitive aging; the dedifferentiation hypothesis of cognitive aging; and the effect of childhood IQ on all-cause and specific mortality, morbidity, and frailty in old age are presented.