The effects of selected presentation variables on the formation of vocational concepts by educable mentally retarded students

Abstract

Eight instructional presentation variables were examined to determine their effects on the acquisition of five curriculum based concepts by 127 educable mentally retarded adolescents who were enrolled in vocational education programs in five Texas communities. Five null hypotheses and 13 sub-hypotheses were tested utilizing data derived from three related experiments. A lesson format, based on the concept teaching principles of D. Cecil Clark (1975), was used to develop the instructional materials for a 30-minute lesson on the identification of five metal threaded fasteners. The instructional materials served to test the effect on learning of six visual presentation modes (line drawings, detailed drawings, photographs, photograms, 35mm. color transparencies, and actual objects) and two variations in complexity of language (a high frequency of technical terms versus a low frequency of technical terms). In Experiment I with five treatment conditions (visual presentation modes) and a control group, it was found that the mean gain score for students assigned to photographs (8.6) was not significantly different from the mean gain score associated with photograms (6 .6), nor was the mean gain score for line drawings (13.9) significantly different from the mean gain score for detailed drawings (9.5). A set of preplanned comparisons utilizing multiple t-ratios did show, however, that the students who received instruction on the critical and noncritical attributes of the five concepts performed significantly better (p < .0005) than students in a control group. Retention of the five concepts on three successive posttests administered at 30-day intervals did not significantly increase or decrease over a sixty-day period..