Relevance theory

There are two ways in which thoughts can be communicated from one person to another. The first way is through the use of strict coding and decoding, which makes explicit use of symbols, rules, and language. The second way is by making interpretive inferences, which communicate to the hearer information that is left implicit.

Relevance theory is a proposal (by Dan Sperber and Deirdre Wilson) that seeks to explain the second method of communication: implicit inferences. It argues that the human mind will instinctively react to an encoded message by considering information that it conceives to be relevant to the message. By "relevance" it is meant whatever allows the most new information to be transmitted in that context on the basis of the least amount of effort required to convey it.

Overview
Sperber and Wilson’s theory begins with some watershed assumptions that are typical of Pragmatic theories. Namely, it agrees that all utterances are encountered in some context, frequently make use of sentences, and that all utterances convey a number of implicatures. In addition, they posit the notion of manifestness, which is when something is grasped either consciously or unconsciously by a person.

They further note that it will be manifest to people who are engaged in inferential communication that each other have the notion of relevance in their minds. This will cause each person engaged in the interaction to arrive at the presumption of relevance, which is the notion that a) implicit messages are relevant enough to be worth bothering to process, and b) the speaker will be as economical as they possibly can be in communicating it.

The core of the theory is the “principle of relevance”, which states that any utterance addressed to someone automatically conveys the presumption of its own optimal relevance. In this way, the vast majority of acts of communication will implicitly make manifest the intent to communicate. However, the actual process of deciphering other implicit interpretations is largely left to the communicators themselves by using mental shorthands, or heuristics.

For Sperber and Wilson, relevance is conceived as relative or subjective, as it depends upon the state of knowledge of a hearer when they encounter an utterance. However, they are quick to note that their theory does not attempt to exhaustively define the concept of "relevance" in everyday use, but tries to show an interesting and important part of human speech.