Relevance theory is a framework for understanding the interpretation of utterances. It was first proposed by Dan Sperber and Deirdre Wilson, and is used within cognitive linguistics and pragmatics. The theory was originally inspired by the work of Paul Grice and developed out of his ideas, but has since become a pragmatic framework in its own right. The seminal book, Relevance, was first published in 1986 and revised in 1995.
The theory takes its name from the principle that "every utterance conveys the information that it is relevant enough for it to be worth the addressee's effort to process it", that is, if I say something to you, you can safely assume that I believe that the conveyed information is worth your effort to listen to and comprehend it; and also that it is "the most relevant one compatible with the communicator's abilities and preferences", that is, I tried to make the utterance as easy to understand as possible, given its information content and my communicative skills.
Other key ingredients of relevance theory are that utterances are ostensive (they draw their addressees' attention to the fact that the communicator wants to convey some information) and inferential (the addressee has to infer what the communicator wanted to convey, based on the utterance's "literal meaning" along with the addressee's real-world knowledge, sensory input, and other information).
Inferences that are intended by the communicator are categorised into explicatures and implicatures. The explicatures of an utterance are what is explicitly said, often supplemented with contextual information: thus, "Susan told me that her kiwis were too sour" might under certain circumstances explicate "Susan told the speaker that the kiwifruit she, Susan, grew were too sour for the judges at the fruit grower's contest". Implicatures are conveyed without actually stating them: the above utterance might for example implicate "Susan needs to be cheered up" and "The speaker wants the addressee to ring Susan and cheer her up".
Relevance theory also attempts to explain figurative language such as hyperbole, metaphor and irony.
Critics have stated that relevance, in the specialised sense used in this theory, is not defined well enough to be measured. Other criticisms include that the theory is too reductionist to account for the large variety of pragmatic phenomena.
Overview Relevance theory aims to explain the well-recognized fact that communicators usually convey much more information with their utterances than what is contained in their literal sense. To this end, Sperber and Wilson argue that acts of human verbal communication are ostensive in that they draw their addressees' attention to the fact that the communicator wants to convey some information. In this way, they automatically assert that they are "relevant" to their addressees. A relevant utterance in this technical sense is one from which many conclusions can be drawn at a low processing cost for the addressee.
The addressee uses the information contained in the utterance together with his expectations about its relevance, his real-world knowledge, as well as sensory input, to infer conclusions about what the communicator wanted to convey. Typically, more conclusions can be drawn if the utterance contains information that is related to what the addressee already knows or believes. In this inference process, the "literal meaning" of the utterance is just one piece of evidence among others.
Sperber and Wilson sum up these properties of verbal communication by calling it ostensive-inferential communication. It is characterized by two layers of intention on part of the communicator: a. The informative intention: The intention to inform an audience of something (to communicate a certain content). b. The communicative intention: The intention to inform the audience of one's informative intention (to draw the audience's attention to one's informative intention).
Definitions To describe the claims of relevance theory on a more rigorous level, we need to define a number of technical terms as introduced by Sperber and Wilson.
Manifestness A fact is manifest to an individual if he is capable of accepting it as true or probably true at the given time.
Cognitive environment The set of all facts that are manifest to an individual. This comprises everything they can perceive, remember or infer, including facts they are not currently aware of.
Cognitive effect An effect on an individual's cognitive environment triggered by "outside" information such as utterances directed at the individual. This includes addition of new facts or beliefs, as well as increase or decrease of the confidence in existing beliefs and their rejection, and also the reorganization of information into schemas or maybe other structures to simplify subsequent processing. Typically, an utterance has more cognitive effects if it contains new information that is somehow related to the addressee's current cognitive environment, so that he can draw conclusions from the combined old and new data.
Positive cognitive effect A cognitive effect that is helpful rather than hindering for the individual (e.g. providing true information as opposed to wrong information). More technically: a cognitive effect that contributes positively to the fulfilment of the individual's cognitive functions and goals.
Relevance of a phenomenon An utterance – or any other observed phenomenon – is relevant to an individual to the extent that its positive cognitive effects on the individual are large and the mental processing effort to achieve these effects is small.
Relevance is a comparative property: the more positive cognitive effects and the less processing effort, the more relevant the utterance.
Relevance of an utterance Here are some examples to illustrate the concept of relevance. If Alice and Bob are planning to go on a trip next weekend and Alice tells Bob (1) Next weekend the weather will be really awful. this is highly relevant to Bob, as he can draw a host of conclusions, modifying his cognitive environment: Alice wants them to rethink their plans and wants to inform Bob of this wish; Bob agrees – or doesn't agree and just wants to bring oilskins; Alice wants to know Bob's opinion on that matter; etc. By contrast, saying (2) The weather was really awful on 19 October 1974 in Cumbria. makes just one piece of new, unrelated information manifest to Bob, and is thus hardly relevant; and (3) The weather is really awful right now. is not relevant as it doesn't tell Bob anything new; he has already seen for himself. Finally, the sentence (4) On the weekend weeks after 19 October 1974 the weather will be really awful. contains largely the same information as (1) but requires more effort to process, and is thus less relevant under this definition.
The two principles of relevance The first or cognitive principle of relevance says that human cognition tends to be geared to the maximisation of relevance. Historically, evolutionary pressure has resulted in cognitive systems that recognise potentially relevant stimuli and try to draw relevant conclusions.
More importantly for the issue at hand, the second or communicative principle of relevance says that every utterance conveys the information that it is
a. relevant enough for it to be worth the addressee's effort to process it. (If the utterance contained too few positive cognitive effects for the addressee in relation to the processing effort needed to achieve these effects, he wouldn't bother processing it, and the communicator needn't have taken the trouble to utter it.) b. the most relevant one compatible with the communicator's abilities and preferences. (Otherwise the communicator would have chosen a more relevant utterance – e.g. one that needs less processing effort and/or achieves more positive cognitive effects on part of the addressee – to convey her meaning. After all, she wants to be understood as easily and reliably as possible.)
This principle is summed up as "Every utterance conveys a presumption of its own optimal relevance". If Alice tells Bob something – anything –, he is entitled to expect that Alice wanted her utterance to be consistent with the communicative principle of relevance. Consequently, if Alice tells Bob something that does not seem to be worth his processing effort, such as sentences (2) or (3) above, or something that seems to be less relevant than Alice could have put it, such as (4), Bob will automatically search for an alternative interpretation. The most easily accessible interpretation that is consistent with the communicative principle of relevance is the one Bob accepts as the right one, and then he stops processing (because any further interpretations would cost him more processing effort and would thus violate condition b).
The constraint that utterances are compatible with the communicator's abilities and preferences accounts for suboptimal communication, such as when the communicator is unable to think of a better phrasing at the moment, as well as for stylistic and cultural preferences (e.g. politeness considerations), withholding information, and lying.
Inferences Explicature
On hearing an utterance, the addressee first concludes that the presumption of optimal relevance is met. He then decodes it, which however yields only very incomplete information. Usually, most of the information conveyed by the utterance has to be inferred. The inference process is based on the decoded meaning, the addressee's knowledge and beliefs, and the context, and is guided by the communicative principle of relevance.
For example, take an utterance (5) Susan told me that her kiwis were too sour.
Information the addressee has to infer includes assignment of referents to indexical expressions For the utterance to be relevant, "Susan" most likely has to refer to a Susan both speaker and addressee know. In the absence of other possible female referents, the pronoun "her" has to refer to Susan. (In a different context, as when (5) is preceded by "Lucy didn't like the food at the banquet", a different inference would be drawn.) disambiguation of ambiguous expressions Possible interpretations involving sour kiwifruit are far more accessible than ones involving sour birds; and even if the sentence were about birds it would not provide enough context to satisfy condition a of the communicative principle of relevance. enrichment of semantically incomplete expressions The possessive "her kiwis" could refer to kiwis Susan ate, kiwis she bought, kiwis she grew herself, etc. Following (5) by "So she didn't win the fruit grower's contest" establishes relevance of the latter option. "too sour" also needs to be specified to make sense. Given the above context, the kiwis must be too sour for the judges at the contest.
Consequently, the explicit meaning of (5) is (6) Susan told the speaker that the kiwifruit she, Susan, grew were too sour for the judges at the fruit grower's contest. This is called an explicature of (5).
Implicature
Further inferences that cannot be understood as specifications and extensions of the original utterance are implicatures. If speaker and addressee know that Susan is a sore loser, an implicature of (5) could be (7) Susan needs to be cheered up. The distinction between explicature and implicature is not always clear-cut. For example, the inference (8) He drank a bottle of vodka and fell into a stupor. → He drank a bottle of vodka and consequently fell into a stupor.