While clinical assessment is still based largely either on the clinical or on the statistical diagnostic model, in recent years alternative models of assessment have appeared: the experimental, the behavioral, the decision-making, and the operations-research models. They are briefly described and critically evaluated. The new models emphasize the importance of the relevance of psychological information for specific clinical decisions. They point to the need for psychologists to participate more closely in everyday decision processes concerning treatment and other actions with remedial implications.Psychologists have become concerned about the status of the psychodiagnostic or assessment function of clinical psychology (Carson, 1958;Holt, 1967). Breger (1968) has even argued that there is no need for diagnostic testing. However, surveys indicate that diagnostic testing remains the most frequently demanded function in hospitals (Swenson, 1965;Wellner, 1968).Psychologists and clinicians seldom discuss the nature of diagnosis. It seems to be such an established part of clinical practice that few clinicians stop to consider what is meant by it and whether it is an essential prerequisite to medical practice (Engle & Davis, 1963). The introduction of behavioral techniques into the clinic and other developments in psychology and in the field of scientific decision making have resulted in the appearance of several new models for psychological assessment which challenge the diagnostic model. They are the experimental, the behavioral, the decision-making, and the operationsresearch models. These are discussed in turn in the present paper.
DIAGNOSTIC MODELThis model is well known and only a brief summary is here offered. The medical diagnostic model might be characterized as the determination of the illness, disease, or dysfunction which accounts for the symptoms, signs, complaints, or behavior deemed to be an aspect of ill health. One must always add that the aim of this process is treatment. Thus