When interpreting a discourse, the addressee typically expects that the signer communicates in a cooperative way. According to the cooperative principle, participants in a conversation cooperate to achieve mutual conversational goals. Under this line of research, the signer is expected to obey a set of rules, known as conversational maxims. There are four cooperative maxims: quantity, quality, relevance, and manner. The maxim of quantity states that the quantity of delivered information must be appropriate. According to the maxim of quality, the delivered information must be true and supported by adequate evidence. The maxim of relevance consists in making contributions that are relevant to what has been said before. The fourth maxim concerns manner: the delivered information must be brief, clear, and unambiguous.
In some cases, signers might decide to violate a maxim in a way that interlocutors clearly understand the violation. In such situations, a conversational implicature arises.
Importantly, implicatures are context-dependent: in the presence of different contexts, the same implicature might not arise.
Very common conversational implicatures are scalar implicatures, which are often related to a set of lexical expressions and are ordered by entailment, such as the quantifiers some, most and all (LEXICON 3.10.2). The signer knows that, in the entailment scale, some is lower than most and lower than all. The choice to use amore specific item (e.g. most) suggests that the stronger characterisation (e.g. all) does not hold. An example of a sentence with the use of most is presented below.
student majority study be_engaged
‘Most of the students are engaged in studying.’
In the sentence above, the conversational implicature is that ‘not all the students are engaged’. However, if the signer adds a second utterance, such as in the example below, the previously established conversational implicature is cancelled.
student majority be_engaged study palm_up all be_engaged
‘Most of the students are engaged in study, actually all the students are engaged.’
Unlike conversational implicatures, conventional implicatures (PRAGMATICS 7.2) and presuppositions (PRAGMATICS 7.3) cannot be cancelled.
Another property of conversational implicatures is that they can be reinforced, as in the example below. Here we can see that the expression more_than not fulfils the function of reinforcing the implicature (“no more than the established number”).
giannia ixa car two exist more_than not
‘Gianni has two cars and no more than two.’
Conversational implicatures are also not detachable. Given a specific context and a specific proposition, the same implicatures will arise. As in the example below, where the conversational implicature enhances the possibility that tomorrow it will not rain.
tomorrow rain maybe be_possible
‘Maybe tomorrow it will rain.’