Morphophonological influences on the comprehension of subject-verb agreement: an ERP study

Event-related potentials were used to study whether factors known to influence subject-verb number agreement in production exert analogous effects on sentence comprehension. Participants read Dutch sentences containing subject-verb number agreement errors while their brainwaves were measured. The determiner of the singular head noun could be ambiguous or unambiguous in number and the modifier ("local") noun could be plural or singular. Both ambiguity and number match affect error rates in production. We expected evoked potentials in response to the verb to be modulated by number ambiguity; larger effects were expected when the sentences started with an unambiguous determiner. When the local noun was singular, we observed a more negative wave elicited by the incorrect verbs compared to the correct verbs in the 350-400 ms time-window. This effect was largest when the head noun phrase contained no number ambiguity. When the local noun was plural the waves were more positive for incorrect verbs than for correct verbs in the 600-650 ms time-window. Again this effect was largest when the head noun phrase contained no number ambiguity. Most importantly, the results show that agreement computation in comprehension is influenced by the same factors as in production. We further suggest that in the sentences with a singular local noun there is a shallow analysis of the sentence, but the sentences with a plural local noun require a deeper syntactic analysis.