Stories of Individual Differences. Longitudinal Studies in Developmental Psychology, 1920-1980

Yves Hänggi

Advisor: Caroline Arni


Beginning in the 1920s, initially in the United States and subsequently in Europe, an array of psychological longitudinal studies got initiated. They aimed at a comprehensive understanding of human development. Bigger samples and the fact that they observed, tested and measured the same individuals repeatedly over a longer period, distinguished those studies from the child observations of the 19th century. By exploring the hardly investigated history of those longitudinal studies the project focuses a crucial site of the history of development. That is to say the longitudinal studies converged two conceptualizations of development, which had emerged seperately from each other in the 19th century: While the theorization efforts of child psychology had put forth development as an orderly, teleological process, biomedical research of innate anomalies and diseases had composed development as a susceptible, contingent event. Led by a historical epistemological perspective and focusing on two cases, the project explores how longitudinal studies linked those two aspects of development by putting forth the idea of an individual course of development, which they let appear by measuring samples repeatedly. Hence there was a genuinely developmental explanation of individual differences on hand. Like the pathological the normal was now thought of in historical terms. Against this backdrop the project not only challenges a narrative which interpretes the institutionalization of developmental psychology as a break but pursues the history of developmental psychology beyond its establishment.