A pioneering retrospective and longitudinal study of temperament begun by Alexander Thomas (1914-2000) and Stella Chess (1914-2007) in the late 1950s. Parent descriptors of their infants‚aa behaviours in questionnaires and interviews resulted in the identification of nine dimensions of temperament, subsequently reduced to three broad categories (‘easy babies’, ‘difficult babies’, and ‘slow-to-warm up babies’). As the children became older, interviews with teachers and tests of the children were added. The subjects of the NYLS have been followed up to middle age.
See Early Childhood Longitudinal Studies (ECLS), Longitudinal studies, National Child Development Study (NCDS), National Educational Longitudinal Surveys (NELS), National Institute for Child Health and Human Development Study of Early Child Care (NICHD-SECC), National Longitudinal Study of Adolescent Health (AddHealth), National Longitudinal Survey of Children and Youth (NLSCY), National Longitudinal Survey of Youth (NLSY), Temperament