The effect of instructional method on symbol acquisition by students with severe disabilities

Abstract

An alternating treatments design nested within a multiple baseline across symbol pairs was used to investigate the effect of two instructional methods (discrete trial and incidental teaching) on the rate of symbol acquisition for two ten-year old boys with autism and severe disabilities. The effect of color enhancement of symbols on learning rate was also investigated.

Coloring strategy did not appear to make a significant difference in the students' ability to learn or functionally use symbols. While one student used only background enhanced symbols functionally, the other student functionally used one symbol from each of the coloring strategies. No significant difference in rate of symbol acquisition was noted between coloring strategies for either student.

Results related to generalization were mixed. For the student with autism, only symbols taught via incidental teaching were used functionally. The second student used one symbol taught through each instructional strategy functionally.

Mixed results were also obtained regarding the comparison of discrete trial and incidental teaching strategies. While no statistical difference was found in the effectiveness of the two strategies, visual analysis of the data indicated that for the student with autism, incidental teaching resulted in a more consistent increase in performance over time. Both students showed a statistically significant level of perseveration on specific symbol locations. This resulted in a high level of variability in performance and may have resulted in the under-estimation of potential differences between instructional strategies.

Results related to time efficiency were statistically significant, however they were also mixed. In one case, discrete trial teaching required significantly less time, in the other incidental teaching required less time. In terms of challenging behavior, incidental teaching was consistently associated with lower rates of challenging behavior.

As neither methodology was clearly superior, and both appeared to have at least some benefit for both students, a focus on the effects of mixing the two methodologies appears to be the most appropriate direction for future research.