Despite strong consensus that early, specialized intervention for children with Autism Spectrum Disorder (ASD) can have a dramatic impact on outcomes, the public health system's capacity to provide such services is severely challenged by the rapid rise in ASD prevalence. The long-term goal of this study is to improve services and outcomes for children with early signs of ASD by testing the effectiveness of training EI providers to deliver an evidence-based, inexpensive, caregiver-mediated intervention that can improve child and family outcomes as well as mitigate the substantial economic costs associated with ASD. This research will take place within an existing community-based infrastructure: the Part C Early Intervention (EI) service delivery system. Part C is publicly funded, available throughout the country, and serves children under age 3 who have developmental delays or disabilities, and their families. Currently, the effectiveness of EI services is limited by high practice variation and infrequent use of evidence-based interventions. The study objective is to improve services and outcomes for children with early signs of ASD and their families. Toward that end, the investigators are conducting a randomized controlled trial (RCT) examining the effectiveness of training EI providers to deliver Reciprocal Imitation Training (RIT), as compared to an active control condition. RIT is a naturalistic developmental behavioral intervention (NDBI) that is ideally suited for EI settings because it is low intensity, play-based, easy to learn and implement, and can be taught to families for their independent use, thus increasing intervention dosage. The investigators will conduct this study within the context of an effectiveness-implementation hybrid type 1 design to gather evidence that will be essential for implementing RIT in other communities if it is found to improve child and caregiver outcomes.

EI providers will be randomly assigned to either the RIT training (n=30) or an active control condition (n=30). Providers in both conditions will complete surveys about their caseloads and intervention practices at 5 time points, once before their training workshops and four times after the workshop (1, 3, 6, and 12 months post-training). Providers assigned to the RIT training condition will receive an 8-hour virtual workshop on the rationale for, and implementation of, RIT with families, with an emphasis on caregiver coaching. Providers assigned to the active control condition ('Daily Routines') will receive a 3-hour virtual workshop on methods for helping caregivers increase their children's participation and social engagement during everyday home routines. Providers in this condition will be able to receive RIT training at the end of the study.

Providers in both conditions will also invite 2 families from their caseload to participate in this study. Caregiver recruitment and data collection will begin immediately after the training workshops are conducted with providers. Enrolled families must speak and read English or Spanish and have a child between 18 and 30 months for whom ASD is either suspected or confirmed. Caregiver participation involves having one EI session videotaped, completing survey measures at 3 time points, and conducting a play-based assessment in their homes (with coaching) at the same 3 time points: baseline, 3 months later, and 6 months post-baseline. The play-based assessment will measure children's motor imitation, social communication, caregiver fidelity to RIT, and caregiver use of child-centered interaction strategies. At the same 3 timepoints, caregivers will complete measures about their parenting stress and parenting self-efficacy, their child's social communication and language, and any additional services the child is receiving. The child's adaptive behavior will be measured via caregiver-interview at baseline and 6-months. Caregivers will also report on the 'top concerns' they have about their child at baseline, and will rate the severity of these concerns monthly thereafter. Family-level "RIT dosage" will also be measured via a weekly Dosage Log sent to caregivers via text message. Caregiver-reported satisfaction with treatment and the study, as well as caregiver-reported child ASD symptomatology will be collected at their final visit (6-months after enrollment).