Abstract
Adaptations to a partner perceived to be conversationally incompetent can be heard in speech to children, the hard-of-hearing, foreigners, speakers with certain speech defects, the aged, and hospital patients. These adaptations may be controlled partially by the actual performance of partners in conversations, through influences on perceived ability. The first half of this paper describes specific changes in children's conversational abilities in early childhood, which in turn may serve to alter how their partners judge their abilities to understand. The second half of the paper addresses the evidence regarding the level and types of changes in adult speech to children as the child's ability changes.