In 1931 the newly-founded Scottish Council for Research in Education (SCRE) took the decision to describe the mental ability of Scotland’s children. This was a part of Scotland’s unique contribution to an international collaboration called the International Examinations Inquiry. The Mental Survey Committee was formed and, after finding no practicable method of obtaining a representative sample, decided to instead test the entire nation. A test was needed that could easily be administered to large groups of children with minimum instruction. Godfrey Thomson’s Moray House Test No. 12 was chosen, and on June 1, 1932 almost all children born in 1921 and attending school in Scotland were given the same mental test with the same instructions: 87, 498 children in total. A small number was tested on a different day. Scotland remains the only country in the world to have tested the entire population in this way.
By the 1940s, a debate was raging in Scotland and England around the relationship between intelligence and fertility. There were fears of a dysgenic trend in intelligence because it was perceived that more professional people were having fewer children. The Royal Commission on Population was formed to investigate through the use of census information. Their work was helped by the Population Investigation Committee (PIC) who, along with the Eugenics Society, had a real concern that the inverse relationship between intelligence and fertility would result in an overall lowering of the population’s intelligence. In order to investigate this, members of the PIC worked closely with SCRE to instigate a second Scottish Mental Survey, this time in 1947, to enable direct comparison with the 1932 Survey. To the surprise of all, the 70,805 participants in the SMS1947 scored on average higher than their predecessors, debunking the theory that the IQ of the population was falling.
Samples of both groups of children were followed up for several years after the Scottish Mental Surveys. As the Moray House Test did not provide IQ scores, 1000 of the 1921-born children were given the Stanford Revision of the Binet Scale (thereafter known as the Binet 1000). This group were followed up into adulthood and information on their occupation, marital status and fertility collated by academics both in Scotland and London – James Maxwell at Moray House and David Glass at LSE.
Critics of the Binet 1000 argued that the sample was not representative of the population due to the selection processes used, and so the follow-up of the SMS1947 was far more rigorous and representative. Two samples were obtained: the 36-day sample, consisting of all children born on the first 3 days of each month, and the 6-day sample, consisting of all children born on the first day of alternate months of 1936. The former provided some background social information while the latter undertook a more detailed IQ test (the Terman-Merrill 1937 Revision of the Binet Test) and provided detailed home, occupational and recreational information for the next 16 years. Again, James Maxwell and SCRE were heavily involved in these studies.
The ledgers containing the results of the Scottish Mental Surveys of 1932 and 1947 were stored by SCRE and were little used by psychologists after the 1960s until the mid-1990s when they were rediscovered by a group of academic researchers in Aberdeen (Professor Lawrence Whalley) and Edinburgh (Professor Ian Deary). It was felt that the ledgers provided access to unique data on childhood ability and afforded the possibility to conduct two important streams of research. First, it was decided to examine the influence of childhood mental ability on future health and quality of life: cognitive epidemiology. Second, the childhood mental test data provided an opportunity to study the contributors to cgange in cognitive fucntions over the human life span: cognitive ageing.
In 1997, the researchers began to recruit survivors of the SMS1932 to form the Aberdeen Birth Cohort 1921 (ABC1921), who were given a variety of cognitive and physical tests as well as some of them resitting the Moray House Test No. 12. From 1999 onwards, they began to recruit the Lothian (Edinburgh) Birth Cohort 1921 (LBC1921). To date, these latter individuals have been seen on up to three separate occasions and have undertaken detailed cognitive assessment (including sitting the MHT at ages 80 and 87!), physical assessment, retinal photography, measures of asymmetry and genetic analysis. The ABC1921 group have been seen on 4 separate occasions within old age.
Follow-up studies of the SMS1947 soon followed and the ABC1936 and LBC1936 were formed. The ABC1936 undertook a half day assessment of cognition and health and to date have been seen on 3 occasions, including many having undergone brain imaging. The LBC1936, consisting of over 1000 survivors of the SMS1947 from the Lothian region, undertook extensive cognitive and physical assessments as well as providing background social & dietary information. This group are presently being followed up as part of the Disconnected Mind project, funded by Help the Aged until 2014, and all will be undergoing magnetic resonance imaging of the brain to identify structural and white matter changes in the brain.