Abstract:
The differential outcomes procedure is a variation on conditional discrimination whereby each stimulus is associated with a unique reinforcer, which has been shown to increase accuracy and speed of acquisition in animals. The aim of this thesis is to evaluate the effectiveness of the differential outcomes procedure in applied settings and determine the parameters – both individual and procedural – under which the differential outcomes procedure can be effective. By translating the differential outcomes procedure to an applied context, where conditional discrimination is commonly used, we hope to find a useful technology for improving conditional discrimination acquisition in children with ID and pervasive developmental disorders. This thesis combines different methods to evaluate the differential outcomes procedure. First, we used meta-analytic methods to quantitatively evaluate the effect of the differential outcomes procedure in humans. This was used to inform human operant research to evaluate the differential outcomes procedure in a controlled lab setting (Chapter III), and single-subject experimental design (SSED) to evaluate the differential outcomes procedure in applied settings with clinical populations (Chapters IV and V). Overall, we found that the DOP is effective in humans. However, the effects were variable across studies. Our quantitative analysis found large effects for the differential outcomes procedure in typically developing children and healthy adults. Our human operant studies, failed to demonstrate that the effect was moderated by stimulus complexity. Our applied studies demonstrated the differential outcomes procedure enhanced acquisition of tacts but not listener responses in clinical populations – children with ID and/or pervasive developmental disorders. Taken together these studies provide evidence that the differential outcomes procedure is effective with humans and can be used with clinical populations to enhance conditional discrimination learning, however, more research is need to fully elucidate when and for whom the differential outcomes procedure is a useful intervention.