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Purpose: This article presents the results of a meta-analysis to determine the effect of augmentative and alternative communication (AAC) on the speech production of individuals with developmental disabilities.
Method: A comprehensive search of the literature published between 1975 and 2003, which included data on speech production before, during, and after AAC intervention, was conducted using a combination of electronic and hand searches.
Results: The review identified 23 studies, involving 67 individuals. Seventeen of these studies did not establish experimental control, thereby limiting the certainty of evidence about speech outcomes. The remaining 6 studies, involving 27 cases, had sufficient methodological rigor for the "best evidence analysis" (cf. R. E. Slavin, 1986). Most of the participants (aged 2-60 years) had mental retardation or autism; the AAC interventions involved instruction in manual signs or nonelectronic aided systems. None of the 27 cases demonstrated decreases in speech production as a result of AAC intervention, 11% showed no change, and the majority (89%) demonstrated gains in speech. For the most part, the gains observed were modest, but these data may underestimate the effect of AAC intervention on speech production because there were ceiling effects.
Conclusions: Future research is needed to better delineate the relationship between AAC intervention and speech production across a wider range of participants and AAC interventions.
KEY WORDS: augmentative and alternative communication, speech production, developmental disabilities, effectiveness, meta-analysis, systematic review
Augmentative and alternative communication (AAC) interventions can benefit individuals with developmental disabilities who have significant speech and language impairments by enhancing their communicative competence (e.g., Light, Binger, Agate, & Ramsay, 1999) and facilitating the development of language skills (e.g., Romski & Sevcik, 1996). Despite these recognized benefits, some parents and professionals are hesitant to initiate AAC interventions because of concerns that AAC will inhibit speech production (e.g., Beukelman, 1987; Silverman, 1995). They worry that AAC may become a "crutch" for individuals with developmental disabilities, negatively impacting the emergence of speech (Dowden & Marriner, 1995), and argue that individuals with developmental disabilities may prefer to use AAC and may not be motivated to learn to use speech to communicate, because they perceive that AAC is an easier way to communicate compared with speech (Glennen & DeCoste, 1997).
Others (Romski & Sevcik, 1996) have proposed a counterargument, positing...