Five educable mentally retarded students in a public school special class were shown four different instructional filmstrips and were given four tests of comprehension. Baseline measures suggested that the students answered from 18 to 24 percent of the comprehension questions correctly. Performance charts and money were then manipulated in an attempt to increase comprehension scores. A multiple baseline design was used to measure the effectiveness of the instructional procedures. Results suggested that correct responding was a function of the contingent consequences presented, and that initial responding might have been due to inappropriately programed performance variables rather than to the intrinsic difficulty level of the instructional materials.
McCarthy et al. (Thu,) studied this question.