Great progress has been made in understanding the production of individual speech sounds but much less is known about the production of prosody. Lexical stress is a type of prosody that reflects the contrast between strong and weak syllables within single words. The ability to achieve this contrastivity shows a protracted developmental trajectory in healthy children and is atypical in some children with autism. How these developmental influences relate to language-specific versus physiological motor-control factors is unknown. This project will address this critical research problem via innovative acoustic investigations. Outcomes will trigger the next generation of speech production models with potential for impact in areas like speech pathology.