Clark began his work in common ground with studying the references in conversation between experts and novices. To develop references in discourse, speakers try to establish the mutual belief that all speakers understand the references to a criterion that is sufficient for the purpose of continuing the discourse. In a conversation between a physician and his patient, for example, the doctor may request, “Contract your deltoid,” making reference to a technical term that the patient may not know. If the patient doesn't know, he will ask, “My deltoid?” and the doctor will clarify, “Raise your right arm.” If the patient does know the reference, he will comply immediately. Throughout these exchanges, speakers supply and acquire expertise. Clark test summarized the process into 3 stages: assessing (directly or in passing finding out the expertise level of the discourse partner), supplying (experts who are addressing novices can expand their contribution to explain the reference), and acquiring expertise (novices speaking to experts acquire knowledge and fill in the gaps during conversation). Perspective is also important to the conversations between experts and novices; as experts gain more expertise their understanding of the topic becomes more broad and abstract, taking on organization that novices cannot follow. When explaining certain concepts to novices, experts also have to take on the perspectives of novices to make the most effective references.
