Treatment Intensity Variables in AAC Interventions for Learners With Autism and/or ID: A Meta-Analysis

Abstract

This systematic review and meta-analysis examined single-case experimental design (SCED) literature on malleable factors related to treatment intensity of augmentative and alternative communication (AAC) instruction with individuals with intellectual disabilities (ID) and/or autism, evaluating the effectiveness of communication production interventions as a function of treatment intensity with consideration of potential moderating factors. Databases were searched through September 2025. Inclusion criteria included AAC interventions; participants with ID and expressive communication disabilities; AAC measures; SCEDs; and English. Articles were screened at title-abstract and full-text stages for inclusion and design quality. We calculated response ratio and baseline-corrected Tau effect sizes, estimated average effects, and tested moderating variables using multivariate, multi-level models. Sixty-nine articles were included, inconsistently reporting participant or treatment intensity variables, though more consistently recently, to a degree that led to null findings. Most treatment intensity variables were not systematically associated with effect magnitude. Massed trials yielded significantly higher effects than spaced/distributed or mixed pacing, though the more frequent implementation of massed trials skews these results. AAC use did not degrade during maintenance, although effects were heterogeneous. Insufficient reporting of treatment intensity variables impeded identification of moderators. Limitations included exclusion of group studies and studies not meeting design standards. A PRISMA-compliant abstract is available at: https://osf.io/r4hgj/ .