Promoting generalization and maintenance in augmentative and alternative communication: a meta-analysis of 20 years of effectiveness research

This synthesis aimed at determining the effectiveness of interventions in augmentative and alternative communication with particular emphasis on strategies that induce generalization and/or maintenance. Fifty single-subject experimental studies, including 232 comparisons of experimental phases, yielded quantitative outcome measures. Interventions were effective in terms of behavior change, generalization, and, although to a lesser degree, maintenance. Using predefined quality indicators to arrive at a best evidence data set, interventions remained effective in changing behavior, whereas generalization and maintenance data could not be interpreted due to the small n. This lack of sufficient best evidence data, along with the prominence of "train and hope" approaches, calls for training of clinical researchers in the breadth of available strategies and training as to how these strategies may be incorporated into treatment procedures. Directions for future research are presented based on identified research gaps and méthodologie issues.