PSYCHOPHYSIOLOGICAL STUDIES IN MENTAL DEFICIENCY
Defects in school and social adjustment, together with low scores on formal psychological tests, constitute the most commonly agreed upon characteristics of mental deficiency and have been the subject of most of the psychological research in this field. Such an emphasis on inadequacies in complex behavioral adjustments is entirely appropriate for workers concerned primarily with the social and educational aspects of mental deficiency. It encourages research on learning, language, and social processes, which should ultimately result in the improvement of the status of the mentally deficient as well as contribute to the understanding of these complex behaviors.
There are other characteristics which, though not as obviously related to educational and social adjustment, may also contribute to an understanding of mental deficiency. Among these characteristics is the generally lower biological status of defectives reflected in the existence of multiple handicaps and in the evidence of brain abnormality, especially in institutionalized patients. These abnormalities have been of major concern to medical research workers studying etiology and somatic therapy, while psychologists have taken the lead in studying the relationship of these defects to behavior. Medical researchers in mental deficiency usually have not been interested in behavior. When they have been, their approach has characteristically focused on the IQ as a major dependent variable. Psychologists have used more refined behavioral measures but have been limited in other ways. Their conceptions of brain injury, for instance, have been very gross.____________________