Children with delayed language onset in the absence of social impairments are diagnosed with a condition called developmental language disorder (DLD). Various theoretical accounts have been proposed to explain the differences in children with autism vs. DLD. However, understanding what underlies delayed language onset in children with ASD and DLD is important to inform psycho-educational intervention approaches and to further clarifying the relation between the two disorders. This study will use both behavioral and electrophysiological experiments to examine the behavioral and brain activity patterns in children with impaired language and social processing vs. those with DLD and typically developing children at different points during development. These studies will better describe both the behavioral responses and neural systems in children with language delay with and without autism, and importantly, follow these children for several years to determine how early language impairment predicts later function in adolescence. Significance: Although it seems very likely that early social-communicative impairments contribute to delayed language onset in many children with ASD, there are many gaps in the understanding of how sound and speech deficits lead to social impairments. A better understanding of how these impairments differ between children with ASD and DLD, on both speech function and brain activity, will lead to better therapeutic interventions and more sophisticated research on the genetic and neurological basis of speech delay.