Linguistic inability or poor performance: Dissociating scalar implicature generation and mismatch in the developing brain

Behavioral investigations of the acquisition of some have shown that children favor its logical interpretation (some and possibly all). Adults, however, use the pragmatic interpretation (some but not all) derived by a scalar implicature. Certain experimental manipulations increase children's rates of adult-like responses, indicating that children are capable of computing implicatures. A functional MRI (fMRI) study examining adults linked the left inferior frontal gyrus (IFG) to implicature computation, and prefrontal regions, the left middle frontal gyrus (MFG), and medial frontal gyrus (MeFG), to processing the mismatch between implicatures and the context in which they were presented. In the current fMRI study, we aimed to determine whether children's failure to give pragmatic interpretations to some results from a failure in implicature computation or in implicature-mismatch processing. We explored children's brain activations with the same experimental task administered to adults. In a region-of-interest analysis, children showed an activational pattern similar to the one observed in adults in the left IFG with increased activations for the implicature conditions. By contrast, in the left MFG, children showed decreased activation for the mismatched implicatures compared with matched and no implicature conditions. No difference between the conditions was observed in the MeFG. For both implicature conditions, no activation in the left IFG was observed when comparing adults and children directly. However, for mismatched implicatures, adults showed greater activation in the prefrontal regions compared with children. Our results suggest that children may have an adult-like computation of implicatures (even when their behavior does not necessarily indicate that), but they fail in resolving implicature-mismatch situations.