Objective: The purpose of this investigation was to determine if the use of a sibling model during structured play therapy would increase participants’ social participation using an AAC device, as evidenced by commenting, compared to using an adult model. Method: This investigation used an Adapted Alternating Treatment Design (AATD) with an n of 1. The primary dependent variable (DV) was the number of communication attempts made, defined as a comment directed toward the parent or sibling with the intent of participating or making a statement using the AAC device. The secondary dependent variable was the number of communication attempts made, defined as a question directed toward the parent or the sibling with the intent of gaining information using the AAC device. The independent variables were sibling-modeling and parent-modeling on an AAC device. The investigation included three phases: baseline, four communication partner training session, and intervention. Results: Data displayed an accelerating trend during both interventions. Percentage of non-overlapping data (PND) for the sibling modeling condition was 100%, while the PND for the parent modeling condition was 83%. Sibling modeling reached the criterionof five occurrences for three consecutive sessions first, in session. Parent modeling, though measurable change was achieved, did not meet the criterion. Social communication, defined as comments, improved for both treatment conditions; however, sibling modeling was more effective than parent modeling. Conclusion: The data supported the initial claim that preschool children with limited verbal skills, whose primary mode of communication is an augmentative and alternative communication (AAC) device, make more communication attempts when receiving AAC therapy with a sibling model, as evidenced by the increase in number of communication attempts (comments) compared to the use of an adult model. The results have future implications for speech-language pathologists (SLPs) providing services to AAC users and training families of AAC users to improve social communication.
