Examining adaptive peer-mediated interventions for preschoolers with autism spectrum disorder and limited or no spoken language: A Sequential Multiple Assignment Randomized Trial - PROJECT SUMMARY Impaired social communication is a core feature of autism spectrum disorder (ASD). This proposal will evaluate a series of peer-mediated interventions for preschool-age children (3 to 6 years) with ASD and limited or no spoken language, using an innovative Sequential Multiple Assignment Randomized Trial (SMART) design. Available evidence supports the beneficial effects of peer-mediated interventions for improving social communication skills in children with ASD.1, 2 Peer-related social competence is vital to a wide range of child outcomes.3 Children who achieve positive peer interactions in preschool show improved social communication and fewer behavioral problems in elementary school.4 In spite of considerable early intervention efforts, approximately 30% of children with ASD remain minimally-verbal in kindergarten5, restricting participation in inclusive activities. Recent studies report improved communication between children with ASD and peers after a speech-generating device (SGD) is included in treatment.6-9 A repertoire of effective interventions that can be applied and modified is necessary to ensure optimal social communication outcomes when children do not make anticipated progress. A strength of the study is that these interventions can be adopted by community- based, early service providers. All participants will receive an adapted Stay-Play-Talk (SPT)7, 10-12 peer- mediated intervention that varies in active ingredients examined by the PI in preliminary studies. Now, with SMART designs, it is possible to test and identify alternative combinations of peer-mediated approaches, such as the addition of a SGD to improve social communication of children with ASD and complex communication needs.7, 8, 13 In the current proposal, 132 preschoolers with ASD (and N=264 peers without disabilities) will be initially randomized to SPT and SGD with spoken peer input only (SPT Basic; peers taught to model language) or SPT and SGD with augmented peer input in which peers are taught to model verbal responses while simultaneously selecting screen icons (SPT Plus; peers taught to use verbal language models concurrently with the SGD). Each child’s response to treatment after 5 weeks will determine that child’s next phase in the SMART design. Children showing a positive response will continue in their originally assigned group. Children who are slow responders after 5 weeks will be randomly assigned to receive added treatment components to improve peer-directed communication (either SPT Plus or SPT Advanced). SPT Advanced adds direct instruction strategies for the children with ASD (i.e., adult prompts, reinforcers, and teaching trials) shown to increase child vocalizations in SGD interventions.9, 14 The use of a SMART design extends our prior work by testing the systematic addition of selected peer-mediated strategies in combination with an SGD8 that allows for flexible application of interventions based on child response measured at important nodal points.15-17 We have assembled an outstanding team of highly qualified investigators with complementary skills in preschool assessment, language intervention, clinical trials, and statistics.