He was forced to stay there during the war in near-famine conditions, discussing German literature with officers in the German occupation force while at the same time helping to protect an escaped Russian prisoner of war who had swum from Guernsey where occupation was harsher.Under some special post-war arrangement, on his return to England he was able to enter University College London, where he was to remain all his working life, and indeed was planning to come and teach on the day before he died He took Psychology but his studies were far more eclectic Influenced by J.B.S. Haldane, he built on his actuarial training to obtain a deep understanding of statistics. However, possibly the greatest intellectual impact on him was A.J Ayer's seminars. He absorbed Ayer's critical style perhaps too thoroughly and applied it in all domains of knowledge that he encountered.In the early 1950s with his statistical background he turned to psychometrics, the study of the measurement of personality and intelligence, and acted as a statistical collaborator for both Hans Eysenck and Cyril Burt. Burt is a discredited figure now, but technically he was highly competent.
He was Editor of the British Journal of Statistical Psychology, where he was later to be followed by Jonckheere.At the time Burt was working on his famous data, or better infamous data, on the intelligence of identical twins reared apart, which for many years provided the cornerstone of the idea that general intelligence, "g", has a very high genetic component. Although Burt did not involve Jonckheere in the project he frequently mentioned that Jonckheere must meet his (Burt's) collaborators, such as "Miss Conway", who have never since been identified. Unsurprisingly, Jonckheere never actually met them and they appear to have been as much a figment of Burt's imagination as the data on which he worked.This was the time in which Jonckheere married his first wife, Joy. (They were to be divorced in 1968.) Intellectually the period culminated for Jonckheere in his development of a new statistical test for detecting trends in so-called categorical data. The test is now extensively used and indeed is incorporated in the most widely adopted statistical package for the behavioural sciences, namely SPSS. During this period Jonckheere was also working on a doctorate, which, naturally for him, was in a different field, namely animal psychology.While Jonckheere retained his interests in the technical aspects of psychometrics, as a psychologist he had become much more interested in how cognitive processes actually develop in the child, rather than how they are measured in some fairly crude way.
Being bilingual in English and French, he was invited to spend the academic year 1956-57 in Geneva at the International Centre for Genetic Epistemology. There he collaborated with Jean Piaget and Benoit Mandelbrot on how children acquire concepts of probability.Piaget was so taken by Jonckheere that he refused to allow him to leave until he could find someone equally clever. Jonckheere's response was to find the brilliant South African ?gr?eymour Papert, later to prove a theorem that held up the development of neural network modelling for 10 years.On his return to London Jonckheere developed a style of organisation of his working life that changed relatively little over the years. He had been made a lecturer in 1951 with special responsibility for lecturing on statistics and animal psychology. By the late 1950s he was lecturing on a wide variety of other topics too. His lectures were much appreciated, but these days would be considered dubious in approach.
