Relevance theory is a framework for understanding utterance interpretation first proposed by Dan Sperber and Deirdre Wilson and used within cognitive linguistics and pragmatics. It was originally inspired by the work of H. Paul Grice and developed out of his ideas, but has since become a pragmatic framework in its own right.
Relevance theory aims to explain the well recognised 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.
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.
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, infer or remember, 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. 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 2312 weeks after 19 October 1974 the weather will be really awful.
contains exactly 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.
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
- 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 to sour for the judges.
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). 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.
has traditionally been seen as an implicature. However, relevance theorist Robyn Carston has argued that implicatures have to be logically independent of explicatures, because the otherwise resulting redundancy would not be consistent with the relevance principle. Therefore, the inference in (8) has to be an explicature, or more specifically a case of enrichment.
Contrasted with the conduit metaphor
There are two ways to conceive of how thoughts are communicated from one person to another. The first way is through the use of strict coding and decoding (such as is used with Morse code), also known as the Shannon-Weaver model. In this approach the speaker/author encodes their thoughts and transmits them to their audience. The audience receives the encoded message and decodes it to arrive at the meaning the speaker/author intended. This can be visualized as follows:
- Speaker's thought/intention ⇒ encoded ⇒ transmitted ⇒ decoded ⇒ intention/thought understood
This is usually referred to as the code model or the conduit metaphor of communication. Human communication, however, is almost never this simple. Context almost always plays a part in communication, as do other factors such as the author's intentions, the relationship between the sender and receiver, and so forth.
The second way of conceiving how thoughts are communicated is by the author/speaker only conveying as much information as is needed in any given context, so that the audience can recover their intended meaning from what was said/written as well as from the context and implications. In this conceptual model, the author takes into account the context of the communication and the mutual cognitive environment between the author and the audience. (That is what the author/speaker thinks that audience already knows.) They then say just enough to communicate what they intend – relying on the audience to fill in the details that they did not explicitly communicate. This can be visualized as follows:
- Speaker's thought/intention ± context-mediated information ⇒ encoded ⇒ transmitted ⇒ decoded ± context-mediated information ⇒ thought/intention understood by hearer (an interpretive resemblance to the speaker's intention)
- Sperber & Wilson (1995:145)
- Sperber & Wilson (1995:108f, 265)
- Sperber & Wilson (1995:50ff)
- Sperber & Wilson (1995:39)
- Sperber & Wilson (1995:153)
- Sperber & Wilson (1995:260)
- Sperber & Wilson (1995:270)
- Wilson & Sperber (2002:258)
- Carston (2002:377)
- Carston (1988:162f)
- Sperber & Wilson (1995:2–9)
- Reddy (1979:284–324)
- Carston, Robyn (1988). "Implicature, Explicature, and Truth-Theoretic Semantics". In Kempson, Ruth. Mental Representations: The Interface between Language and Reality. Cambridge University Press.
- Carston, Robyn (2002). Thoughts and Utterances: The Pragmatics of Explicit Communication. Wiley-Blackwell. ISBN 978-0631214885.
- Reddy, M. J. (1979). "The conduit metaphor – a case of frame conflict in our language about language". In Ortony. Metaphor and Thought. Cambridge University Press.
- Sperber, Dan; Wilson, Deirdre (1995). Relevance: Communication and Cognition. Wiley-Blackwell. ISBN 978-0631198789.
- Wilson, Deirdre; Sperber, Dan (2002). "Relevance Theory" (PDF). UCL Psychology and Language Sciences. Retrieved 22 January 2019.