Dr Ron Gray, from Oxford University, who led the research added that although the differences appeared small, they may well be significant and that lower IQ had been shown to be associated with being socially disadvantaged, having poorer health and even dying younger.

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Mr Gray, formerly of Oxford and now professor of European thought at the London School of Economics, is an extremely clever man.

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The title was held by the late historian Hugh Trevor-Roper, Regius Professor of Modern History at Oxford, and the 18th Century poet Thomas Gray, who was Regius Professor of Modern History at Cambridge.

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