Validity in Psychological Testing and Scientific Realism

Abstract

Recent work in the conceptual foundations of psychometrics has concerned the question of validity. Borsboom and colleagues have challenged what they claim is the dominant theory of validity, that of Samuel Messick. In this paper I present Borsboom et al.’s concept of validity as a property of measurement instruments as well as Messick’s concept of validity as a property of interpretive inferences. I then relate their concepts of validity to scientific realism in the philosophy of science. I argue that there can be valid psychometric tests, in Borsboom et al.’s sense, only if some version of scientific realism is true. I argue that in Borsboom et al.’s and Messick’s approaches to validity, one finds the essential ingredients for a realist philosophy of science in psychological assessment. Borsboom et al. contribute semantic and ontological components while Messick provides the methodological tools for constructing an epistemology of psychological measurement. Though Borsboom et al. present their approach as an alternative to Messick’s, these two approaches to validity are potentially complementary.