Wing-Yee Chow, Colin Phillips
Recent observations of unexpected ERP responses to grammatically well-formed role reversed sentences (the “Semantic P600” phenomenon) have been taken to bear directly on questions about the architecture of the language processing system. This paper evaluates two central pieces of evidence for accounts that propose a syntax-independent semantic composition mechanism, namely, the presence of P600 effects and the absence of N400 effects in role reversed sentences. Experiment 1 examined the relative contribution of the presence of an animacy violation and the semantic relations between words (‘combinability’) to the ERP responses to role-reversed sentences. Experiment 2 examined the ERP responses to role-reversed sentences that are fully animacy-congruous. Results from the two experiments showed that animacy-violated sentences with no plausible non-surface interpretation elicited the same P600 effect as both types of role-reversed sentences; additionally, semantically anomalous target words elicited no N400 effects when they were strongly semantically related to the preceding words, regardless of the presence of animacy violations. Taken together, these findings suggest that the presence of P600s to role-reversed sentences can be attributed to the implausibility of the sentence meaning, and the absence of N400 effects is due to a combination of weak contextual constraints and strong lexical association. The presence of a plausible non-surface interpretation and animacy violations made no unique contribution to the ERP response profiles. Hence, existing ERP findings are compatible with the long-held assumption that online semantic composition is dependent on surface syntax and do not constitute evidence for a syntax-independent semantic composition mechanism.