We have argued for a significant shift in how clinical researchers approach the acquisition of scientific knowledge. Empirical data have been quite consistent with the possibility that terms that are routinely used in clinical inquiry, from neuroticism and extraversion to depression and posttraumatic stress disorder, do not in fact represent meaningful, cohesive psychological constructs; rather, they represent combinations of constructs. As a result, their use in investigations of the validity of constructs or theories is not recommended. To maximize the validity of findings from their inquiries, clinical scientists may be best served by conducting tests with measures of unidimensional, homogeneous constructs. Only measures of such constructs can represent coherent, causally active psychological entities.
