The proposed study (CAIT: Community-based Adaptive Autism Intervention for Toddlers) aims to determine the most optimal sequence of interventions for improving the social- communicative, language and cognitive outcomes of toddlers with autism spectrum disorder (ASD). The target population consists of 2-3 year-old children with ASD who receive community based, publicly funded early intervention in two authentic educational settings in East Harlem and the Bronx, NY known as New York Center for Infants & Toddlers (NYCIT). An expected 300 toddlers with ASD will participate with their community-recruited paraprofessional teaching assistants (TAs) and group leaders (GLs). The study aims to construct the most effective one-year, two-phase, adaptive intervention, in which intervention is individualized based on a child's initial response to intervention. Phase 1, from program entry to either 6 or 12 weeks (randomized), involves 60 minutes daily of an evidence based social communication intervention, JASPER (Joint Attention, Symbolic Play, Engagement & Regulation) delivered 1-on-1 to the child by the trained TA. At end of Phase 1, response to intervention is rated by the GLs for slow or fast improvements of joint engagement (a core deficit in the early development of children with ASD, and a significant indicator of good progress toward improving social communication and language). In Phase 2 (to week 24), toddlers responding slowly are re-randomized to continue with JASPER for 60 minutes per day or augment treatment with direct, structured teaching of social communication targets for 30 minutes and JASPER for another 30 minutes per day. Toddlers responding quickly are given 30 minutes of JASPER and 30 minutes of jasPEER (JASPER with a peer) to further improve socialization and social communication.

This study will use a Sequential Multiple Assignment Randomized Trial (SMART) design to assess when to examine initial response to treatment, as well as whether and how best to augment the current first line, standard of care intervention for children demonstrating a slower response.

First, at program entry, the investigators will assess all toddlers using both standardized and experimental assessments as they enroll in the NYCIT program. After entry assessments, the investigators will randomize each child with equal probability to early response assessment at either six weeks or 12 weeks (timing). This early response assessment will be used to determine whether children are considered fast or slow responders to treatment. Children who are considered early responders will continue to receive JASPER. Children responding slowly to the initial intervention will be randomized to continue JASPER or to add JASPER Plus+ to their JASPER sessions. Approximately 200-300 toddlers (24-36 months) with a diagnosis of ASD, as confirmed by clinical evaluation records required for placement at the NYCIT will participate. Children will be assessed prior to intervention, immediately after Stage 1(early response) at either six or twelve weeks, exit Stage 2 intervention, and follow up.

If teacher/paraprofessional withdraws from the study, all reasonable efforts will be made to place the child with another consenting teacher/paraprofessional. Based on the first two years of trials working with this center, no teacher withdrew mid study. However, a small number of teachers did change positions or took leave (e.g., maternity leave, move for job in another district). In these cases, the child was transferred to another consenting teacher.

SMART Design:

Initial Randomize to Stage 1 Treatment

Stage 1: JASPER (6 weeks)

Early Responders/Slow Responders determined

Stage 2: JASPER (Early Responders only)-A

Slow Responders randomized to Stage 2: JASPER Plus+ + JASPER -B or Stage 2: JASPER (Randomized for slow responders)-C A, B, and C options occur during the following 18 weeks

Exit assessments and Follow up assessments at 3 months post exit

Initial Randomized to Stage 1 Treatment

Stage 1: JASPER (12 weeks)

Early Responders/Slow Responders determined

Stage 2: JASPER (Early Responders only)- D Slow Responders randomized to Stage 2: JASPER Plus+ + JASPER - E or Stage 2: JASPER (Randomized for slow responders)- F D, E, and F options occur during the following 12 weeks

Child Inclusion Criteria:

• diagnosis of ASD based on clinical report or ADOS-2 if needed
• chronological age less than 36 months
• caregiver consent to learn intervention strategies if randomized to either parent condition.

Exclusion Criteria:

• Child has co-morbid disorders such as cerebral palsy or down syndrome.