What do children need to know and do to participate successfully in conversation? First, they must learn to observe some basic conditions for conversation:
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. To be successful, speakers need to assess what their addressees already know (their common ground) and tailor their utterances on that basis. In addition, they need to make clear whether they are asserting or commenting on some state of affairs, making a request for information or for action, or presenting some other speech act (a promise, a threat, a greeting, and so on) or a combination of speech acts. Lastly, all the participants in a conversation need to make their contributions relevant, appropriate to the topic at hand at each stage in the exchange.
Speech acts can be classified into several types (Searle 1975). The main categories that have been described are assertives, directives, commissives, expressives, and declarations. First, with an assertive, speakers convey their belief that a proposition is true. The commonest assertives are straight assertions (e.g., Rod left yesterday), but they can also be introduced by verbs like suggest, hint, swear, flatly state, and so on (e.g., I swear Rod left yesterday).