The effects of uncertainty of occurrence and uncertainty of time—use of catch-trials and preparatory intervals—in simple reaction time (RT) trials were investigated with nonhandicapped and mentally retarded subjects. The results showed that: (a) Catch-trials impaired the performance of this task, (b) catch-trials did not differentiate among groups of subjects, and (c) preparatory intervals differently affected RT latencies of nonhandicapped and mentally retarded subjects. Interpretation of findings suggests that the use of catch-trials induced preparation decrements and that preparation decrements may explain in part the poorer RT performance of retarded subjects.
Request reprints from Paul R. Surburg, Dept. of Physical Education, HPER Building, Indiana University, Bloomington, IN 47405.