Many adults with intellectual disabilities have severe communication impairments and are therefore potential candidates for the use of speech-generating technologies. However, there may be reluctance to prescribe speech-generating devices for adults with intellectual disabilities in the absence of evidence demonstrating that such persons are capable of learning and interested in using this technology. In this chapter, the authors provide an overview of intellectual disability and the use of speech-generating technologies for adults with intellectual disability. This overview is followed by a systematic review of intervention studies that have sought to teach the use of speech-generating technologies to adults with intellectual disability. An overview and review of this type may help to inform and advance evidence-based practice in the provision of communication intervention for adults with intellectual disability.
TopDefining And Describing Intellectual Disability
The term intellectual disability covers a range of more specific disorders and syndromes, all of which share several common diagnostic criteria (Carr & O’Reilly, 2007; Matson, 2007). The essential feature of intellectual disability (or mental retardation) is “significantly sub-average general intellectual functioning . . . accompanied by significant limitations in adaptive functioning . . .” (American Psychiatric Association, 2000, p. 41). The communication domain is one area of adaptive functioning that is often significantly limited in persons with intellectual disability (Sigafoos et al., 2007). Epidemiological and assessment studies consistently show that people with intellectual disabilities often present with major speech, language, and communication problems (Abbeduto, Evans, & Dolan, 2001). The nature and extent of their communication problems depends, in part, on the etiology and severity of intellectual disability (Duker, van Driel, & van Bercken, 2002; Sigafoos et al., 2007).
In terms of etiology, there is some research suggesting that certain intellectual disability syndromes are associated with distinct and possibly unique communication profiles. Duker et al. (2002), for example, compared the communication profiles of individuals with Down syndrome to individuals with Angelman syndrome. They found that individuals with Down syndrome tended to have greater deficits in the communication functions related to requesting and rejecting/protesting in comparison to echoic or imitative functions. The opposite was true of individuals with Angelman syndrome. These data highlight the importance of etiology in designing communication interventions for individuals with intellectual disability.
Intellectual disability is a heterogeneous condition. It is therefore possible that promising interventions for one etiological group, such as communication interventions involving the use of SGDs, may prove unsuitable for another etiological group. In addition to the skills that the individuals present with, consideration of person’s the current and future environments and the communication partners they are expected to interact with in those environments may lead to the selection of an appropriate intervention. Thus consideration of participant characteristics, as noted by Bedrosian (2003), is important when reviewing studies on the use of speech-generating technologies in communication interventions for adults with intellectual disability.