Input capability and speed of processing in mental retardation.

Abstract

The minimum stimulus duration for criterion accuracy and the minimum interval between presentation of a test and presentation of a masking stimulus for criterion accuracy were determined for mildly and moderately retarded adults and normal controls of the same mental and chronological age. The procedure was replicated three times in three separate sessions. Results indicated that both retarded groups required longer stimulus durations as well as longer masking intervals for criterion accuracy than did both the mental age and the chronological age control groups. Results were interpreted as consistent with deficiencies in both iconic storage and speed of information processing in mental retardation. These deficiencies, furthermore, cannot be accounted for on the basis of low mental age. Information processing theory, which assumes human behavior can be analyzed in terms of discrete stages or processes, has opened new avenues of research in psychopathology. In viewing a response as only the end product of a series of processes, it becomes possible to specify the correlates of observed performance deficits more accurately than could otherwise be done. In mental retardation research, for example, considerable controversy has centered around the underlying source of performance deficits related to visual information processing (see Spitz, 1973). One major issue concerns whether observed differences between retarded and nonretarded persons on tasks related to visual processing can be explained solely on the basis of low mental age in the retarded persons (e.g., Galbraith & Gliddon, 1972; Spitz & Thor, 1968; Thor, 1970; Welsandt & Meyer, 1974). Another major unresolved issue concerns which stage or stages of processing are most impaired in retarded persons. Libkuman and Friedrich (1972) spoke of limitations in brief perceptual memory or, as Neisser (1967) called it, iconic