On the value of homogeneous constructs for construct validation, theory testing, and the description of psychopathology.

Abstract

The authors argue for a significant shift in how clinical psychology researchers conduct construct validation and theory validation tests. They argue that sound theory and validation tests can best be conducted on measures of unidimensional or homogeneous constructs. Hierarchical organizations of such constructs are useful descriptively and theoretically, but higher order composites do not refer to definable psychological processes. Application of this perspective to the approach of the Diagnostic and Statistical Manual of Mental Disorders to describing psychopathology calls into doubt the traditional use of the syndromal approach, in which single scores reflect the presence of multidimensional disorders. For many forms of psychological dysfunction, this approach does not appear optimal and may need to be discarded. The authors note that their perspective represents a straightforward application of existing psychometric theory, they demonstrate the practical value of adopting this perspective, and they provide evidence that this shift is already under way among clinical researchers. Description in terms of homogeneous dimensions provides improved validity, utility, and parsimony. In contrast, the use of composite diagnoses can retard scientific progress and hamper clinicians' efforts to understand and treat dysfunction. Keywords valid diagnosis; construct validation; construct definitions; homogeneity; diagnostic progressThis article has two basic aims. The first is to advance the argument that unidimensional construct measures provide the best basis for construct validation tests and theory tests. Validation tests on multidimensional measures, which are composites of related measures, can obscure important psychological processes. Elements of composites can, and do, act differently from one another, so analysis of composite scores combines the potentially different roles of its elements. For that reason, the use of composite scores can lead to unclear conclusions. The second aim is to apply this perspective to the problem of assessing and describing psychopathology. Many psychiatric diagnoses are composites of more than one construct, and so they may not represent meaningful psychological entities for most scientific purposes. Their use can interfere with clinical practice. We therefore advocate a new approach to

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