Speed of information-processing and structural limitations by mentally retarded and dual-diagnosed retarded-schizophrenic persons.

Three experiments were conducted in an investigation of information-processing capabilities of mentally retarded adults, nonretarded children (mental age control), and nonretarded adults (chronological age control). In all experiments, one of two target stimuli was presented to the center and to the right or left of central fixation. Subjects were required to detect the presence of a stimulus in a yes-no forced-choice paradigm (Experiment 1), identify which of the two targets had been presented in a forced-choice discrimination paradigm (Experiment 2), or distinguish between the targets in a forced-choice discrimination task when the target was preceded by, presented stimultaneously with, or followed by a patterned noninformational masking stimulus. The findings support the theory of a structural defect in mentally retarded persons that results in slow information-processing.