It's all in your head: Effects of expertise on real-time access to knowledge during written sentence processing

Real-time sentence processing involves connecting linguistic input with knowledge. Here, we ask how variability in semantic memory (specific domain knowledge) may influence semantic access in realtime sentence processing. We recorded EEG while participants more/less knowledgeable about the narrative world of Harry Potter (HP) read sentences. In Experiment 1, all participants showed N400 predictability effects for general-knowledge sentences, but only those with high HP knowledge showed predictability effects for sentences about Harry Potter. This effect was driven by graded brain responses to predictable endings as a function of knowledge. Experiment 2 revealed greater semantic activation (inferred from N400 effects) for HP items participants reported knowing. Highknowledge participants also showed greater semantic activation for items they reported not knowing/remembering. These findings suggest that amount and/or functional organization of knowledge has real-time consequences on written sentence processing and implicate implicit/partial access to domain knowledge for experts when information is not explicitly recalled.