sessing anxiety level in defectives would constitute a necessary first step in a research program in this area. One phase of such validation work could very feasibly involve extensive observation of the performances in complex and simple learning situations of defectives identified as low-anxious and high-anxious by the assessment technique in question. In addition, the study of the effects of high and low stress on defectives' performance in such learning situations could shed considerable light on the utility of the Hull-Spence SHR X D formulation for understanding defectives' behavior. This general area has hardly been touched by research workers interested in mental deficiency.
Theory-oriented behavioral research using defectives as subjects is often criticized on the basis that the experimenters involved are not really interested in mental deficiency. A typical expression of this attitude may be found in a paper by McPherson ( 1958). After summarizing 14 studies published in the decade prior to 1958 and noting the upsurge in interest in the experimental approach to the study of learning in defectives, McPherson (p. 876) commented as follows: "This impression of increased interest in the experimental approach to learning and mental deficiency is negated somewhat by the realization that four of these papers have utilized mental defectives because of their usefulness for learning data and theory per se, rather than because of an interest in this type of learner."
Persons sharing this attitude rarely, if ever, are explicit about exactly what constitutes a "genuine interest" in the defective learner. The present writer would take the position that the psychologist as scientist is basically concerned with behavioral processes, or, put in other terms, with the discovery of laws that will allow him to predict behavior. Whether the behavior in question happens to be that of the mentally defective, the normal, or some infrahuman species, the scientist's obligation is to make use of the frame of reference which he considers most promising in the way of leading him to such laws. If, in the search for behavioral laws applicable to the behavior of defectives, one is led to abandon more traditional ways of studying defectives' learning processes in favor of a different approach (e.g., the application of Hull-Spence or any other theory), it is difficult to understand why this amounts to a lack of interest in the defective, per se.
In the previous section of this chapter, three approaches within the Hull-Spence framework to the study of defectives' behavior were described and illustrated. All three--the curve-fitting approach, the gross comparative approach, and the noncomparative approach--show considerable promise of being of reciprocal benefit to both the field of behavior theory and the field of mental deficiency, in the present writer's opinion. To the extent that such research helps to verify any of the various Hull-Spence postulates, or to show in what fashion they are inadequate, to this extent will behavior theory benefit from the activity. And to whatever extent behavior theory benefits, the understanding of defectives' behavior cannot help but be