The concept of conversational implicature was introduced by British philosopher Paul Grice (1975) to show how meaning expressed by the speaker (speaker meaning), not directly encoded in the words, can be inferred (recognized) by the hearer. For example, if speaker A says ‘Has John arrived?’, and speaker B responds ‘There is a blue car in the driveway’, one can infer, under the appropriate circumstances and based on shared assumptions between the interlocutors, that John has arrived. Grice observed that conversational exchanges consist of cooperative efforts recognized by each participant. As a result, he proposed the Cooperative Principle: ʻMake your conversational contribution such as is required, at the stage at which it occurs, by the accepted purpose or direction of the talk exchange in which you are engagedʼ (1975: 45). Grice proposed four conversational maxims governing the rules of conversation: (1) quantity: do not make your contribution more informative than is required; (2) quality: do not say what you believe to be false or that for which you lack evidence; (3) relation: be relevant; and, (4) manner: be brief and orderly.
Research in L2 implicature shows that beginning learners are less able to understand and use implicatures in the L2. For example, Roever (2013) examined the use of implicature for the purposes of diagnostic assessment among high proficiency learners of English and NSs of English, using a 10-item multiple-choice task to test two types of implicature, idiosyncratic (general conversational implicature) and formulaic (indirect criticism, irony, scalar implicature). As expected, results showed that NSs scored signifgicantly higher than the learners.
In a series of studies, Bouton (1992, 1994, 1999) examined the ability of advanced ESL (English as a Second Language) learners to interpret various types of implicatures in English using a cross-sectional design. The studies focused on pragmatic comprehension and used a multiple-choice questionnaire in fully contextualized situations to elicit the data. Learners with different L1 backgrounds were divided into three groups according to their length of residence (LR) in the United States: 17 months, 33 months, and 4 to 7 years. It was found that learners’ ability to interpret implicatures in American English seemed to have been achieved during the first 17-month period. When the mean scores between the 17-month group (18.06) and the 33-month group (18.80) were compared, no significant differences were found, although the mean scores were slightly higher in the group with a longer LR. Thus, it was concluded that learners’ ability to interpret implicatures seemed to have been achieved during the first 17 months of their stay; after 17 months in the L2 culture, the learners’ ability to interpret most implicatures stabilized, but progress was slow. However, due to the large spread between groups, it is difficult to know precisely at what point pragmatic development took place, or whether pragmatic development increased over the 17 months and by the end of this period learners’ pragmatic ability to comprehend most implicatures stabilized. More research on L2 implicaure is needed to further examine the processes by which learners comprehend pragmatic meaning through implicature, including the ability to recognize irony, metaphor, and sarcasm.