What do children need to know and do to participate successfully in conversation? First, they must learn to observe some basic conditions for conversation:

• Speaker and addressee must share a joint focus of attention during the conversational exchange and take account of common ground.

• Speakers must take account of what their addressees know and tailor their utterances accordingly.

• Speakers must choose speech acts that are appropriate for the meanings they intend to convey.

• Participants in a conversation must listen to what others say so they can each make appropriate, relevant contributions when they take a turn.

Establishing joint attention requires speakers to make sure that the addressee is attending both to the speaker and to whatever the speaker is attending to. This condition is essential to successful reference, whether by a child or an adult. Joint attention is supplemented by both physical and conversational co-presence (H. Clark 1996). Physical co-presence is particularly important for young children, since, together with joint attention, it helps solve the mapping problem when they encounter unfamiliar terms. And conversational co-presence gains in importance as children's lexical knowledge and general linguistic skills expand, since they become better able to use whatever linguistic as well as nonlinguistic information speakers offer in the course of conversation.

Speakers also need to be able to convey their intentions, and this requires that their addressees be able to recognize the speech acts they produce.