A Meta-Analysis of Single Case Research Studies on Aided Augmentative and Alternative Communication Systems with Individuals with Autism Spectrum Disorders

Many individuals with autism cannot speak or cannot speak intelligibly. A variety of aided augmentative and alternative communication
(AAC) approaches have been investigated. Most of the research on these approaches has been single-case research, with small
numbers of participants. The purpose of this investigation was to meta-analyze the single case research on the use of aided
AAC with individuals with autism spectrum disorders (ASD). Twenty-four single-case studies were analyzed via an effect size
measure, the Improvement Rate Difference (IRD). Three research questions were investigated concerning the overall impact of
AAC interventions on targeted behavioral outcomes, effects of AAC interventions on individual targeted behavioral outcomes,
and effects of three types of AAC interventions. Results indicated that, overall, aided AAC interventions had large effects
on targeted behavioral outcomes in individuals with ASD. AAC interventions had positive effects on all of the targeted behavioral
outcome; however, effects were greater for communication skills than other categories of skills. Effects of the Picture Exchange
Communication System and speech-generating devices were larger than those for other picture-based systems, though picture-based
systems did have small effects.