Hemispheric asymmetry of strongly constrained and weakly constrained bridging inferences: An ERP study

Readers must be able to make inferences to maintain coherence during reading. Prior research suggests that the cerebral hemispheres process inferences differently depending on level of textual constraint, however, it is not clear when these hemispheric differences occur during reading. The current study investigates how levels of textual constraint influences the hemispheric processing of bridging inferences. Participants read texts promoting a strongly constrained (Experiment 1) or weakly-constrained (Experiment 2) bridging inference and then performed a lexical decision for targets presented to either the left or right hemisphere. Using event-related potential (ERP) analysis, N400 and P600 waveforms were examined during the target presentation. For strongly constrained inferences, a larger N400 effect was found in the right hemisphere than the left hemisphere. For weakly constrained inferences, there was a larger N400 effect overall, but no differences between the hemispheres. In addition, no hemispheric differences were observed for the P600 waveform between the strongly and weakly constrained inferences. Thus, hemispheric asymmetries seem to occur during the early stages of text processing when readers might generate both strongly and weakly-constrained inferences.