The Scottish Mental Surveys of 1932 and 1947 tested almost every child born in 1921 and 1936 respectively attending school in Scotland. The first Scottish Mental Survey, organised and undertaken by the Scottish Council for Research in Education, was undertaken as part of Scotland's contribution to the International Examinations Inquiry, with the aim of describing the mental abilities of Scottish children. For this purpose, the Moray House Test No. 12 was chosen, and 87, 498 children were given the test on June 1, 1932.

By the 1940s, debate was rife regarding the perceived differential birth rate, and the Royal Commission on Population was formed to investigate this, assisted by the Population Investigation Committee (PIC), and the Eugenics Society, who were both concerned that the nations' intelligence levels were lowering as a direct result of professional people having less children than those from disadvantaged backgrounds. The purpose of the second Scottish Mental Survey, therefore, was to enable comparison with the 1932 Scottish Mental Survey. There were 70,805 participants in the second Scottish Mental Survey, which again used a test designed by Thomson and his colleagues, and the results showed a slight improvement in the nation's intelligence.