g. when they are presented with a picture of two men with hats, and told to point to the man with the hat), they still select a referent, and they do not tell the experimenter that s/he did not give them enough information (Ackerman, 1981, Beal and Flavell, 1982, Robinson and Robinson, Cyclopamine 1982 and Robinson and Whittaker, 1985; among many others;

see Plumert, 1996, and Beck, Robinson, & Freeth, 2008, for recent developments and an overview of previous work). Although the research on ambiguity detection has not interacted with that on implicature, both converge on the finding that 5-to-6-year-old children fail to employ the first maxim of Quantity in an adult-like way. Nevertheless, much younger children succeed with many of the Anti-infection Compound Library screening preconditions of pragmatic inferencing, such as attributing and monitoring intentions, tracking their interlocutor’s epistemic state, and counterfactual reasoning (see Clark, 2003, Csibra and Gergely, 2009 and Tomasello, 1992; among others). Therefore, the failure of school-age children with implicatures and ambiguity detection is puzzling. In this paper we investigate why 5-to-6-year-old children fail with informativeness. Our approach has a theoretical and an experimental component. The theoretical part

discusses three major points. First, we argue that scalar and non-scalar quantity implicatures are both derived by the same inferential process, and therefore we would not expect one type of implicature to be privileged over the other in acquisition. Second, we show that sensitivity to informativeness is a precondition for implicature derivation, and therefore that informativeness must be considered when interpreting studies that purport to document competence with implicatures (or a lack thereof). Third, we observe that sensitivity to informativeness TCL and the derivation of quantity implicatures are context-dependent and conversational in nature.

We conclude that researchers testing pragmatic competence should be aware that participants may be tolerant towards pragmatic infelicity and not penalise it to the same extent as logical contradiction, and should design test materials accordingly. In the experimental part of the paper, we demonstrate that 5- to 6-year-old English-speaking children are perfectly competent with informativeness, both with scalar and non-scalar expressions. However, they are also tolerant of pragmatic violations. This previously unacknowledged tendency towards pragmatic tolerance has significantly masked children’s actual competence with the first maxim of Quantity in a variety of tasks, including the referential communication tasks. In the following sections we discuss why the type of implicature may be important in the study of acquisition (Section 2.1), the distinction between sensitivity to informativeness and implicature generation (Section 2.2), and why participants may tolerate pragmatic infelicity (Section 2.3). With the exceptions of Barner et al.