Conceptualizing changes in behavior in intervention research: The range of possible changes model.

Abstract

An international movement has focused on identifying evidence-based interventions: Interventions that were developed to change psychological constructs, and have evidence from controlled studies on their behalf. However, inconsistent findings within individual intervention studies and among multiple studies of the same intervention raise critical problems for interpreting the evidence, and deciding when and whether an intervention is evidence-based. A theoretical and methodological framework (Range of Possible Changes [RPC] Model) is proposed to guide the study of change in intervention research. We recommend that future quantitative reviews of the research literature use the RPC Model to conceptualize, examine, and classify the available evidence for interventions. Further, future research should adopt the RPC Model to both develop theory-driven hypotheses and conduct examinations of the instances in which interventions may or may not change psychological constructs. Keywordsefficacy; effectiveness; range of possible changes; intervention; treatment The terms efficacy or effectiveness denote the study of whether interventions can successfully change specific psychological constructs or behaviors (e.g., Hoagwood, Hibbs, Brent, & Jensen, 1995;Kazdin, 2000;Lambert & Ogles, 2004). 1 An overriding goal of intervention research is to identify evidence-based interventions: Evidence from controlled experiments suggests these interventions change constructs they were developed to change. Researchers have developed classification systems through which a given intervention can be identified as evidence-based, based on prior well-controlled experimental outcome studies examining the intervention (e.g., Lonigan, Elbert, & Johnson, 1998;Nathan & Gorman, 2002;Roth & Fonagy, 2005). Upon scrutiny, the supportive evidence raises Correspondence regarding this manuscript should be addressed to Alan E. Kazdin, Child Study Center, Yale University School of Medicine, 230 S. Frontage Road, New Haven, CT 06520-7900. 1 The intervention literature often distinguishes between the terms efficacy and effectiveness by the setting in which changes in constructs occur. Specifically, efficacy research examines whether an intervention can change psychological constructs under controlled experimental conditions. In contrast, effectiveness research examines whether an intervention can change psychological constructs in more naturalistic settings outside the research laboratory. Despite these differences in settings, both of these research literatures examine the ability of interventions to change multidimensional constructs. Thus, the conceptual and methodological framework we propose generally applies to the study of change in multidimensional constructs in intervention research. At the same time, the evidence we cite in support of our proposed framework is largely gleaned from the efficacy literature, particularly because of its longer history of examination and replication, relative to the effectiveness literature. Thus, it is possible...

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