The records were discovered in the Edinburgh offices of the Scottish Council for Research in Education and have been used by researchers into the effects of ageing. Hundreds of volunteers have been traced and retested on the same questions in Aberdeen and Edinburgh.

They scored a bit better than they did at 11, and differences in mental ability remain constant throughout life. In one of the Edinburgh retests, a “pupil” recorded a perfect score.

The 1932 data on 87,498 children, which are still being analysed with the results of another national test of 70,805 11-year-olds in 1947, were obtained by a distinguished trio of researchers: James Drever, Edinburgh University’s first psychology professor, Sir Godfrey Thomson, professor of education and a world pioneer in measuring intelligence, and Robert Rusk, the research council’s director.

On Monday, June 1, 1932, all but a tiny proportion of the nation’s 11-year olds sat a test based on Sir Godfrey’s Moray House Tests as used in the English 11-plus examinations.

Ian Deary, professor of differential psychology at Edinburgh University, who has looked at the results from the volunteer survivors, says that the common view of old age as a period of mental decline is mistaken.

“Change would be a better description,” Professor Deary says. “We want to find out what it is in life’s experiences, involvement in society and so on that leads some people to making improvements with age rather than declining.”

Picking out factors that maintain thinking skills can show what leads to a generally healthy old age, he says. The research council data are unique in allowing researchers to measure not jut how older people perform but how they measure against their performance as children.

The interest of Professor Deary and Lawrence Whalley, professor of mental health at Aberdeen University, in changes in cognition throughout life was whetted by tracking down the 1932 results.

Professor Deary accepts that the elderly volunteers do not necessarily form a truly representative sample of the original 87,000. Many took the initiative in responding to advertisements and all have shown a basic ability, that of surviving into old age. But the SCRE’s information, which is being computerised, is richer than other international studies such as a Canadian university’s follow-up to tests on recruits to the Forces in the Second World War.

Valerie Wilson, the research council’s director, says: “It is exciting to look through these black-bound ledgers, to see the meticulous way in which the results are recorded by school and by authority and to visualise the co-operation which must have existed then among teachers, education authorities and the organising committee in SCRE.”

She adds: “This part of our educational history is not just an archive.” It and the 1947 survey results give “a unique opportunity which few other countries possess. We hope we will all learn from the data by working in multidisciplinary teams from psychology and public health and that our findings will contribute to our understanding of complex social issues.”

The Scottish Executive has given pound;70,000 to the research project. Professor Deary hopes that the Medical Research Council will support a follow-up of the 1947 tests because “these people are an interesting group”.

He adds: “They are in their sixties, and retirement is now seen as an active period, part of the lifelong learning which is emphasised by government.”