One of the central aspects of language use is the process of referring -- speakers refer to people, places, things, and ideas, and then say things about them, and in order for communication to be successful, the listener must know what the speaker is referring to. At the same time, however, human beings have limited time, energy, and patience, and generally desire to make their communicative interchanges as economical as possible. One way to make communication more efficient is to use a shorter, less specific form of reference, such as a pronoun, when the referent is accessible to the listener. When there might be some doubt about the referent, however, the speaker needs to use a longer, more specific form of reference, such as a name or description. This tension between communication and efficiency is reflected in and embodied by Grice's maxim of quantity: "Make your contribution as informative as is required...[but not] more informative than is required" (Grice, 1975).