Beginning in 1956, Stella Chess and Alexander Thomas tracked the lives of 133 children from infancy to young adulthood, examining in detail their psychological development over a twenty-five-year period. The result was the groundbreaking New York Longitudinal Study. This book, first published in 1984, presents a complete report of the study, including analyses of the data and exploration of such fundamental questions as gender differences, antecedents of adult behavior patterns, and factors that contribute to depression and other disorders. Special emphasis is given to the clinical evaluation and treatment of patients with behavioral abnormalities. The authors discuss key findings: the important role of parental guidance, the continuities and discontinuities across developmental stages, the crucial effects of temperament on psychological development, and the usefulness of a “goodness of fit” model for understanding the relationship between person and environment and for describing the evolution of behavior disorders.