Systematic Review of Speech Generating Devices for Aphasia

The purpose of this chapter is to integrate and synthesize, using a meta-analytic approach, the research literature on the effectiveness of augmentative and alternative communication (AAC) intervention using speech generating devices (SGDs) for people with aphasia. Many individuals with little or no functional speech as a result of severe aphasia rely on non-speech communication systems to augment or replace natural speech. These systems include SGDs and software programs that produce synthetic speech upon activation. Based on this quantitative review, the following conclusions are evident. The first is that the existing state of knowledge on whether AAC interventions using SGDs work for people with aphasia is seriously affected not only because of the lack of data but also because most of the available data are compromised because of serious internal validity concerns. Keeping in mind this first conclusion as a context, the second conclusion is that AAC intervention options that utilize SGDs seem to be effective in changing the dependent variables in the experimental contexts. However, the variability among dependent measures across studies and of results within and across studies precludes meta-analytic techniques. Thus, any statements as to the effectiveness of AAC interventions using SGDs for persons with aphasia cannot be made yet.