A poor boy made good

Opening the joint British Academy and British Psychological Society lecture with a picture of a nondescript Edinburgh property, Professor Ian Deary said 'This is just a story, about this house, and the clutter I found in it.' But what 'clutter': imagine becoming mildly obsessed with a psychologist from the past, someone who was world famous but who faded into obscurity. Then imagine getting a call from his great niece, to say that his only son's house was being sold and you should get down there. You arrive just in time to save hundreds of books, lecture notes and letters from the skip.

Deary was understandably cock- a-hoop at this turn of events, and it allowed him to spin a yarn of fascinating, luxurious texture, weaving the personal threads from the Godfrey Thomson archive into a rich extension of his hero's empirical efforts.

Thomson was a 'lad o' pairts' – a poor boy made good who never lost sight of the goal of raising others out of disadvantage. He described his work, as Professor of Education at the University of Edinburgh for more than 25 years, as falling into 'three parts, (not of course quite separate) concerned with (a) fitting psychophysical curves, (b) the social and geographical distribution of intelligence and the influence of the differential birthrate, and (c) the factorial analysis of ability; and these are, with a wide overlap, representative of three successive chronological periods.'

It was perhaps the second of these parts that most spurred Thomson and this lecture. Handwritten and typed lectures, perfectly preserved in that treasure trove Deary found, mapped out Thomson's mission to find and educate children from poor backgrounds. He saw education as the 'food of the Gods', and was a firm believer in comprehensive education to the age of 16, of equal cost to all ('the same amount should be spent on each individual during his lifetime, disregarding entirely both his needs and his abilities'). Thomson said: 'Nothing can shake my belief that every child ought to have an equal chance of any kind of education in open competition with other children, uninfluenced by the wealth or position of its parents.'

Not that Thomson believed all were equal. 'It is abundantly clear', he told Dundee University College in 1930, 'that there must be, in a world grown complex and mobile, some system of labelling people in as harmless a manner as possible with the record of what they have proved capable of doing.' The differential birth rate was never far from his thoughts: 'The more capable classes of the community marry later and have smaller families than the less capable, and this problem is in my opinion the most important social problem we have with us today.' But despite being a member of the Eugenics Society, Thomson didn't seem like your average eugenicist: 'The educator… must give the best education they are capable of enjoying to everyone, even if the consequence should be that the highest intelligence should be slowly bred out of the race.'

Thomson's research group in 'Room 70' in Moray House College at the University of Edinburgh was an IQ-test industry, churning out more than nine million IQ tests in some years, testing a large chunk of England's 11-year-olds. He gave one of his Moray House Tests of intelligence to the Scottish Council for Research in Education (SCRE) for the 'Scottish Mental Survey of 1932'. On Monday 1 June 1932 SCRE tested 87,498 children – about 95 per cent of Scottish children born in 1921. 'Scotland is the only nation to have tested an entire population's intelligence,' Deary said, 'and they did it all in a morning'.

Fifteen years later, the UK's Population Investigation Committee was similarly worried about the differential birth rate: was the nation breeding out its intelligence? So, with Thomson as Chairman, SCRE did it all again: they tested 70,805 1936-born children in June 1947. IQ had gone up, not down: possibly an early demonstration of the 'Flynn effect' of rising intelligence between cohorts, and confirmation that, as Deary said, 'they decided it was OK for the working classes to have children'. Follow-ups of the 1947 survey were published until 1969, and then the money ran out.

Which is where Deary picks up the baton. 'We have, we hope,' said Thomson in 1948, 'begun something which succeeding generations will carry on', and carry on Deary and his team have, in the most remarkable of longitudinal studies. Working with SCRE to computerise the data in the ledgers, they have tracked down thousands of the original participants and hit them with a barrage of tests covering all manner of cognitive, biological and social measures. The result: dozens of new papers (some of the earlier ones are summarised in an article for The Psychologist in October 2005).

The findings came thick and fast, each supported by a snippet from Thomson's lectures or correspondence. Childhood IQ has a significant impact on survival up to age 76; cognitive change from childhood to old age seems to be affected by the APOE e4 allele; childhood IQ does not predict later satisfaction with life; physical fitness predicts cognitive ability at age 79 over and above IQ at 11; more intelligent, more 'dependable' children live longer; biomarkers such as C-reactive protein sometimes show 'reverse causation' in their association with cognition in old age; and brain white matter tract integrity is a neural foundation of general intelligence. Paper after paper, finding after finding, with the spectre of Professor Sir Godfrey Thomson hanging over them all. And there is no end in sight. The really interesting thing about the 1947 survey, said Deary, was that it provided a base for subsequent studies. Especially important, he said, was a small sub-study that followed up 1208 people, every year, for another 16 years. Deary and his team have embarked on a new study, '6 day sample: Scotland in miniature', which is finding those people and sending them an awful lot of kit and questionnaires.

Where does the apparently tireless Deary find his energy? The answer should, by now, be obvious, and there it is in the words of Godfrey Thomson from 1954:

'You may think – you probably do think – that my message is rather a grim one. Go on studying, I have said. Never rest on your oars, I have said. But the fact is there is no greater pleasure than comes from work. The skilful craftsman has a pleasure denied to the labourer. The master of a subject, or one who at least can understand and be understood by the masters, has a like pleasure. And with mastery, won in most cases before thirty, comes leisure which can be truly enjoyed, not leisure stolen from duty.'