Response-stimulus interval performance of moderately retarded institutionalized subjects.

Based on previous dual reaction-time research with nonretarded and mildly retarded subjects, the expectancy- and capacity-limit hypotheses for the psychological refractory period effect were tested with moderately retarded subjects. The design included regular-irregular procedure, response-stimulus interval, signal, and hand-preference variable levels. The finding of a psychological refractory period effect at the 250-msec response-stimulus interval was consistent with past related research. The moderately retarded subjects indicated a capacity limitation, resulting in the psychological refractory period effect at the rapid response-stimulus interval. Previous researchers working with nonretarded and mildly retarded subjects have suggested an expectancy explanation for the psychological refractory period. This inconsistency in study findings was interpreted on the basis of an organismic confound. Methodological issues were also presented.