Parent language input is crucial for child language development. Therefore, there has been considerable interest in documenting the kinds of language children hear from their parents and other caregivers. Prior research shows that parents tune their language to children’s abilities, and well-tuned input is important for children’s language comprehension. This project is based on a theoretical framework that predicts that the degree of tuning is affected by similarities and differences between parents and children. The project tests this theory by examining whether autistic and non-autistic parents speak differently when interacting with their children. Studying these differences in tuning informs broader theories about the mechanisms supporting language development. This project also supports translational science by laying the groundwork for helping to improve interventions that support language development in children. This project uses two kinds of methods to study language input to children. The first method involves surveying parents to ask them how they talk with their children, and about what kind of language they believe supports their child's language development. The second method involves recording parents and children as they play together using a protocol designed to elicit a variety of child behaviors, including turn-taking, pretend play, and making requests of the parent. Parent language input during these play sessions is analyzed to measure different lan