Dichotic-listening task performance of mildly mentally retarded and nonretarded individuals

An investigation of hemispheric lateralization of mildly mentally retarded individuals was undertaken employing the dichotic-listening paradigm. Exclusively right-handed, right-eyed, and right-footed equal-CA, equal-MA, and mildly retarded subjects were required to recognize and reject dichotic presentation-probe stimulus combinations of words and tones correctly. The dichotic presentation-probe stimulus technique was employed to minimize the influence of memory and to equate methodologically for the handling of the verbal (spoken digits) and nonverbal (complex tones) stimuli. The findings revealed a pattern of dichotic performance that was similar for the three subject groups. A right-ear advantage was obtained for the verbal stimuli; and a left-ear advantage, for the nonverbal stimuli. Performance accuracy, however, was significantly poorer for the mildly retarded subjects relative to the nonretarded subjects. Structural vs. control process differences in the information-processing system were discussed.