Monitoring in language perception: The effect of misspellings of words in highly constrained sentences.

We present evidence for a monitoring process in language perception at the word level, reflected by a P600. This P600 is triggered when a conflict evolves because the brain encounters an unexpected linguistic item when another item is highly expected. To resolve this conflict between representations, the brain monitors the input to check for possible processing errors. A P600 was hypothesized to occur after orthographic anomalies, like pseudohomophones, in particular when the word from which the pseudohomophone is derived is highly expected. This hypothesis was tested by recording ERPs while participants read high-cloze sentences ('In that library the pupils borrow books ....') and low-cloze sentences ('The pillows are stuffed with books ....'). In a pretest, the high-cloze sentences were produced by more than 90% of the subjects, while the low-cloze sentences were never produced. In half of the sentences, the critical word books was replaced by a pseudohomophone (e.g., bouks), which in the high-cloze sentences orthographically and phonologically resembles the highly expected word. Consistent with the monitoring hypothesis, only pseudohomophones in high-cloze sentences elicited a widely distributed P600 effect while pseudohomophones in low-cloze sentences did not. A standard N400 effect of cloze probability occurred both for words and pseudohomophones. The present ERP results support the view that there is a process of monitoring that takes place in language perception which is reflected by the P600. It occurs whenever a conflict between a strong tendency to accept and one to reject a word brings the cognitive system in state of indecision.