MMPI-Rorschach interrelationships: proposed criteria for evaluating explanatory models

An extensive empirical literature, spanning 50 years and 45 published investigations, leads to the conclusion that the Rorschach and the Minnesota Multiphasic Personality Inventory (MMPI) bear little or no meaningful relationship to each other. An inherent tension exists between these empirical findings and the widespread clinical practice of integrating MMPI and Rorschach results. At least three perspectives have been advanced concerning the relationship between these two instruments. One view holds that variables from the two measures will demonstrate significant patterns of convergence only in carefully designed research studies that involve specific, well-constructed and theoretically derived predictions. A second view postulates that although variables from the Rorschach and MMPI do not bear a high intercorrelation with each other, these variables may be combined to contribute significantly to the prediction of outcome variance. In this view, the combined use of the two instruments yields clinically useful increases in incremental validity not achievable by the use of either instrument in isolation. A third approach is reflected in the proposition that although the MMPI and Rorschach do not produce significant interrelationships under general conditions, meaningful relationships may be yielded under specific psychometric conditions, for example, under conditions in which the response styles are consistently displayed across those two instruments. This article will review research evidence related to each of these perspectives, with particular emphasis on the importance of clearly specifying the criteria to be applied in evaluating these models. The concepts of parsimony and heuristic value are proposed for these evaluation purposes.