The long-term study goal is to experimentally evaluate the components (and likely active ingredients) of early language interventions for young children with Down syndrome (DS). The overall objective is to determine how single-word and telegraphic simplification affects real-time language processing and word learning in young children with DS (relative to full, grammatical utterances). The proposed project will investigate three specific aims: 1) Determine how single-word and telegraphic simplification affects language processing. 2) Determine how single-word and telegraphic simplification affects word learning. 3) Evaluate child characteristics that may moderate the effects of linguistic simplification on language processing and word learning. Aim 1 will test the hypothesis that children with DS will process grammatical utterances faster and more accurately than telegraphic or single-word utterances. Aim 2 will test the hypothesis that overall, children will demonstrate better word learning in the grammatical compared to the single-word and telegraphic conditions. Aim 3 will test the hypothesis that receptive language and nonverbal cognitive abilities will be significant moderators, such that children with stronger linguistic and cognitive skills will show the greatest benefit from grammatical input but children with lower linguistic and cognitive scores will perform similarly across conditions.