This is a supplement to project 5R01DC007428-07. Compared to typically developing children, it is not known to what degree language development in children with autism follows the same developmental rules or whether autistic children achieve language comprehension via different routes. Using a novel visual fixation approach called Intermodal Preferential Looking (IPL), the study investigates language comprehension in young children who have recently been diagnosed with ASD and are about to begin an Applied Behavior Analysis (ABA) program. In this longitudinal study, a baseline assessment will be taken before ABA treatment (at 18-42 months of age) and will then be followed by assessments at 4-month intervals for 2+years, with a final assessment at 6-8 years. This project may pinpoint subtle deficits and strengths in the language of children with autism as well as illuminate different developmental pathways in their language acquisition, both of which may guide new early-intervention and treatment protocols.