This paper provides novel experimental evidence for a scalar implicature approach to the plurality inferences that are associated with English plural morphology (Emily fed giraffes -> Emily fed more than one giraffe). Using a Truth Value Judgment Task, we show that both adults and 4–5-year-old children compute more plurality inferences in upward-entailing than downward-entailing environments, but children compute fewer plurality inferences overall than adults do. These findings are consistent with previous research demonstrating children’s relative insensitivity to scalar implicatures. We discuss the implications of these findings for theories of plurality inferences, and for the acquisition of scalar inferences more generally.

The nature of presupposition projection from the scope of quantificational expressions, particularly negative ones, continues to be both theoretically and empirically controversial. We experimentally investigate the interpretation of sentences like None of the bears won the race, which could in principle be associated with three projection options, giving rise to: an existential reading, on which at least one of the bears participated and none won; a universal reading, on which all of the bears participated and none won; and a presuppositionless reading on which none of the bears both participated and won. We used a covered box task to investigate English-speaking adults’ and children’s interpretations of such sentences. The results from the adult participants provide empirical evidence for all three readings; the results from the child participants, however, reveal no evidence for the existential reading. We discuss our results in light of competing theoretical accounts, focusing on options for reconciling the theories with the experimental data from both adults and children.

Presuppositions and scalar implicatures are traditionally considered to be distinct phenomena, but recent accounts analyze (at least some of) the former as the latter. All else being equal, this “scalar implicature approach to presuppositions” predicts uniform behavior for the two types of inferences. Initial experimental studies comparing them yielded conflicting results. While some found a difference in the Response Time (RT) patterns of scalar implicatures and presuppositions, others found them to be uniform. We argue that the difference in outcomes is attributable to a difference in the type of response being measured: RTs associated with acceptance and rejection responses seem to pattern in opposite ways. Next, we report on a series of experiments to support this, and to compare the behavior of the two inferences more comprehensively. Experiments Ia and Ib look at both acceptance and rejection responses for both inference types, and find uniform patterns once the acceptance vs. rejection variable is factored in. Experiment II adds a new dimension by testing for the influence of prosody on the two inference types, and in this regard a clear difference between them emerges, posing a first substantive challenge to the scalar implicature approach to presuppositions. A third set of experiments investigates yet another prediction of this approach, according to which the presuppositional inference is introduced as a simple entailment in affirmative contexts. This predicts that these presuppositional inferences behave parallel to other entailments. Experiment IIIa compares rejections of affirmative sentences based on either their presuppositional inference or their entailed content and finds that they differ, with greater RTs for the former. As an additional control, Experiments IIIb and IIIc test for parallel differences between two entailments associated with always, which yield uniform results. In sum, while Experiments Ia and Ib are in line with previous findings that presuppositions and scalar implicatures under negation show uniform response time patterns, the differences found in Experiments II and IIIa-c pose a substantial challenge to approaches assimilating the two phenomena, while being entirely in line with the traditional perspective of seeing them as distinct.