ABSTRACT
Alexander Thomas and Stella Chess have had a lifelong professional interest in the study of individual differences in development. My own association with them coincided with the inception of the centerpiece of this interest, the New York Longitudinal Study (NYLS). As a medical student moonlighting as a research assistant, I had the great good fortune to participate, together with their collaborators, Herbert Birch and Sam Korn, in the development of methods of data collection and analysis that permitted the definition of individual differences in temperament. One of the most robust findings of this ongoing investigation of the developmental course of temperament organization in a sample of 133 children born to middle-class parents living in New York City and its surrounding suburbs during the mid-1950s is the association between the constellation of “difficult” temperamental attributes and the emergence of behavior disorder. The identification of “difficult” temperament as a condition of risk has had far-reaching implications for the understanding of the pathogenesis and treatment, as well as for the prevention, of psychopathology during childhood. Clinicians and researchers alike have sought to further clarify mechanisms that operate to enhance the deleterious consequences of “difficult temperament” or diminish its impact. Children born prematurely are also at increased risk of delayed, deviant, or disordered development—and it is particularly fitting that a selected review of factors involved in individual differences among low-birth-weight children be included in a collection of papers honoring Chess and Thomas's contributions to child development and child psychiatry.
