Work

Commentaries

Year: 2004

Type: article

Abstract: We are honored to have the opportunity to offer a few words in response to Molenaar’s manifesto (this issue) calling for the return of the individual to scientific psychology. His arguments are clearly articulated, strongly supported, and quite timely, particularly given the recent surge in popularity of longitudinal studies of individual developmental trajectories. Despite our enthusiasm for both his theoretical and statistical perspectives, we would like to briefly articulate a somewhat different view. We do so for two reasons. First, if we simply agreed with his manifesto, this would make for a rather boring commentary and we would rather not bore you. Second, we do not perceive our current set of interindividual variation (IEV) methodologies to be as limited as Molenaar seems to imply. More specifically, Molenaar makes the argument that (a) scientific psychology is almost exclusively based on statistical methods designed for the study of IEV. (b) individual development is defined by processes that are inherently characterized by intraindividual variation (IAV). ergo (c) IEV statistical methods cannot be validly applied to the study of individual development. We agree with Molenaar that there can be a dangerous disjoint between theory and statistics and we have made related arguments elsewhere (Curran & Willoughby. 2003). However, we also believe that existing IEV methodologies can be validly used to gain important insights into the behavior of both individuals and groups. Indeed, we believe that the application of IEV methodologies to data comprised of samples of individuals with the goal of making generalizations to broader populations is a cornerstone of empirical science. To better articulate our perspective, we begin by considering the distinction between internal and external validity.

Source: Measurement Interdisciplinary Research and Perspectives

DOI: 10.1207/s15366359mea0204_2