i18.
M. Shayer and D. Ginsburg, “Thirty Years On—A Larger Anti-Flynn effect? (II): 13- and 14-year-olds. Piagetian tests of formal operations norms 1976–2006/7”, British Journal of Educational Psychology, vol 79, part 3, 2009, pp 409–418. The research was referring to the formal operational stage of cognitive development, when children start to learn how to think abstractly, and to use logic in drawing conclusions—that is, how to process reality and develop judgment. Shayer’s research shows that children’s performance at the lower—“creative operational” stage is actually improved. This stage carries out tasks such as sorting objects, and understanding properties such as size and shape. This classification of cognitive development is based on the work of Jean Piaget, which is surveyed in, for instance, Jean Piaget (1923–1979), The Essential Piaget, edited by Howard E. Gruber and J. Jacques Vonèche. For a press account of Shayer’s findings, see Jessica Shepherd, “Teenagers of yesteryear ‘were brighter’”, The Guardian, 27 October 2008, available at www.theguardian.com/education/2008/oct/27/teenagers-less-bright .