Michael Wadsworth directed the first birth cohort study until 2006, reconfiguring it as a study of physical and mental change with age, adding a study of the following generation, and the collection of DNA, and writing a history of its findings during the first 36 years in their historical and social context in The Imprint of Time .John Bynner directed the Centre for Longitudinal Studies and the 1958 and 1970 cohort studies within a comparative life course study framework until 2003. He also directed the Wider Benefits of Learning Research Centre and the National Research and Development Centre for Adult Literacy and Numeracy.