The body of research on reading instruction and intervention for children who use AAC is small, but continuing to grow. This literature is small, in part, because it is conducted with a low prevalence population. This highlights the importance of maintaining high quality research standards when working with this population by providing descriptions of participants’ characteristics prior to instruction, descriptions of experimenter designed or modified standardized assessments, and using strong research designs.
Each of the studies we reviewed included several of these important characteristics. For example, all of the studies described participants’ speech intelligibility, although Fallon et al. (2004)
did so with the most detailed description and objective procedure. Likewise, each study mentioned extant reading skills, but only a few of those using experimenter-designed reading measures provided detailed descriptions of how those measures were constructed and administered (i.e., Blischak et al., 2004
; Fallon et al., 2004
; Millar et al., 2004
). Consequently, it is difficult to build a cumulative knowledge base because of the wide variety of information and assessments reported. For example, no two studies used the same procedure to assess intelligibility, and numerous measures of early literacy skills were used across studies. Consistent and detailed reporting of measures that have been agreed upon in the field would help build a needed, coherent, and cumulative knowledge base.
A strong suit of this group of studies was the use of experimental single-subject designs; 7 of the 8 studies did so (Blischak et al., 2004
; Coleman-Martin et al., 2005
; Fallon et al., 2004
; Heller et al., 2002
; Johnston et al., 2009
; Millar et al., 2004
; Truxler & O'Keefe, 2007
). In addition, four articles included maintenance and generalization phases or items (Blischak et al., 2004
; Fallon et al., 2004
; Johnston et al., 2009
; Millar et al., 2004
). The study by Fallon et al. (2004)
was the only one we reviewed that included each of the components described previously, met the minimum standards of evidence established by the WWC, provided strong evidence
of intervention effects, and moderate evidence
of generalization. Their five participants had steady baselines and demonstrated increased word reading only after intervention began. Furthermore, they did this in both reading probes and in book-reading contexts. Finally, 3 of the 5 participants demonstrated generalization by reading novel words composed of letters targeted in the intervention. In fact, the results of this study, along with those of Millar et al. (2004)
were used to develop a literacy curriculum designed for children who use AAC (Light, McNaughton, Weyer, & Karg, 2008
). The Accessible Literacy Learning
curriculum (Light & McNaughton, 2009
) incorporates the instructional strategies and materials shown to be effective in these studies and is therefore a good example of research informing practice.
There is much work to do in the area of reading intervention for children who use AAC. First, there is a strong need for standardized assessments of both phonological awareness and reading that do not require speech responses. Although we have discussed several modifications that can be made to phonological awareness and reading assessments, there have been few attempts to assess the validity of these new assessments by making comparisons to established assessments.
The importance of valid assessments becomes apparent when considering differences in task requirements among three word-reading tasks (i.e., the unmodified task and two modified tasks that do not require speech). The unmodified task requires the discrimination of printed words that are presented one by one, and does not constrain responses to a small number of choices. Neither modified task has both of these characteristics. One modified task involves a spoken word as the sample and printed words as choices (e.g., Truxler & O'Keefe, 2007
). Like unmodified reading, correct responses demonstrate relations between speech and print. Unlike reading, correct responding might depend on the presence of the printed-word choices or even the specific printed words that are used as incorrect choices. A second modified task involves a printed-word sample with pictures as choices (e.g., Fallon et al., 2004
). Like reading, this task requires the discrimination of printed words presented one by one. The spoken word is not directly involved in the task, however, thus this is not a direct measure of relations between speech and sound. These points are not meant as criticisms of these procedures, as speech responses are not possible. Consequently, it may be helpful to use both modified reading tasks, as together the two tasks would include more components of the unmodified word-reading task.
Similar considerations of validity arise when making other modifications described previously. For example, the modified phoneme blending task differs from the unmodified CTOPP (Wagner et al., 1999
) in that selecting the picture requires the comprehension of the spoken word, and also that the child’s name for a picture must be the same as that of the developers of the test. Likewise, when having children choose letters from an array for a letter– sound knowledge task, instead of producing the phoneme, selections can be correct by chance. Furthermore, using an array of answer choices—be it pictures, letters, or printed words—allows children to compare correct and incorrect choices. This is not possible when individual printed words are presented, and thus fundamentally changes the nature of the task.
Researchers have attempted to validate some assessments for people who use AAC. One, the Assessment of Phonological Awareness and Reading
(APAR; Iacono & Cupples, 2002
), is available online in print and digital formats. The APAR measures reading using word recognition, nonword recognition, and word comprehension subscales, and phonological awareness using phoneme blending, phoneme counting, and sound-matching subscales. Iacono and Cupples (2004)
found evidence of construct validity of the APAR in a study of 40 adults with significant disabilities. The APAR, however, has not been widely adopted (see Hart, Scherz, Apel, & Hodson, 2007
, for one example) and its validity for use with children has yet to be established. In a second example, Gillam, Fargo, Foley, and Olszewski (2011)
published validity data from children with typical development in dynamic phoneme-deletion task that used pictures as a response mode. Results indicated high construct validity, as performance on the dynamic phoneme deletion task was highly correlated to a deletion task that required speech responses and to other reading tasks. These studies represent important first steps in developing valid assessments with uniform stimuli for children who use AAC.
Second, there is a strong need for replication of results to bolster external validity. The single-subject studies that were reviewed here answered questions about whether, and to what extent, specific instruction affected phonological awareness and reading skills for the study participants (Horner et al., 2005
). But what is the generality of these outcomes to other participants? Single-subject designs derive their strength from replication. Ultimately, a research program aimed at the development of instruction seeks to determine not only whether the instruction is effective, but also to determine the skills that the learner must already have to benefit from the instruction. Unfortunately, the literature currently contains so few replications of any given procedure that the generality of the outcomes across participants with different characteristics has not been established.
One way to address this issue is to compile the results of single subject-design studies using meta-analysis strategies. Shadish, Rindskopf, and Hedges (2008)
and Kratochwill et al. (2010)
discuss strategies for such meta-analyses, a full discussion of which is outside the scope of this review. They offer the following recommendations for researchers using single-subject designs. First, +unstandardized outcomes (i.e., raw scores) using the same metric and on the same scale are preferred because of the ease at which these can be compared within and across studies. Second, when unstandardized scores on the same scale are not available, regression based approaches to calculating standard scores are preferable (see Kratochwill et al., 2010
, for a discussion). Summaries across cases and across studies, such as means and standard deviations, can be calculated when common metrics are used. The potential for summarizing data highlights the importance of common measures. These summaries would allow researchers to make judgments, based on effect sizes, about which interventions are the most effective for children with particular profiles. Ultimately, what is learned from these analyses can be used to inform large-scale intervention studies with a focus on generalizability to the larger population of children who use AAC. Doing this would require large multisite research programs similar to those used in research on interventions for reading disabilities in children who are typically developing (e.g., Morris et al., 2010
Finally, the field of reading research with children who use AAC would benefit from the formation of an online database to aggregate results, similar to those used by researchers and clinicians in other research areas, such as the National Outcomes Measurement System (NOMS; American Speech-Language-Hearing Association) and the Child Language Data Exchange System (CHILDES; MacWhinney, 1996
). Both databases allow researchers and clinicians to submit data that can be used by others to answer broad research questions. Because of its emphasis on intervention, the NOMS database can help researchers and clinicians answer questions ranging from which intervention approaches are appropriate for individual children to larger questions about which interventions are most effective overall. Another strong suit of NOMS is that all who submit data to the database are required to use a set of uniform measures. This enables many data points to be aggregated easily so that the overall effectiveness of particular intervention strategies can be evaluated. The availability of a similar database for reading research with children who use AAC would beneficial for clinicians, educators, and researchers alike.
Currently the evidence base for reading interventions for children who use AAC consists of a small group of single-subject-design studies that use different measures and teaching strategies and demonstrate varying degrees of success. There remains a strong need to develop standard phonological awareness and reading assessments with agreed upon sets of items, both in terms of targets and distractors, to answer questions about the effectiveness of interventions. There also is a need to replicate the results of effective reading interventions across different contexts and groups of children, in single-subject studies and ultimately in larger multisite clinical trials. These represent important and necessary steps in creating an empirically supported evidence base for reading instruction for children who use AAC.