Parsing of sentences in a language with varying word order: Word-by-word variations of processing demands are revealed by event-related brain potentials

Event-related brain potentials (ERPs) were recorded while native speakers read German sentences in which the order of the sentence elements subject, indirect object, and direct object was systematically varied. All sentences were legal grammatical constructions. Sentences were presented word by word and a question on the role assignments had to be answered 5 s after the presentation of the final word or each sentence. Behavioral data confirmed previous findings showing that sentences whose word order deviates from the canonical sequence of subject, indirect and direct object are more difficult to process. ERPs revealed several effects which differed in their antecedent conditions, topography, and timing: (1) Anticipating a question which taxes episodic verbal knowledge was accompanied by a pronounced tonic negative shift having a left anterior maximum. (2) Article which function as case markers in German evoked a transient, left anterior negativity whenever they indicated that a noun phase sequence would not continue in its canonical order. (3) Nouns which follow case markers at noncanonical positions were accompanied by an enlarged transient posterior positivity. (4) Processing of words at terminal positions in sentences with a noncanonical word order was accompanied by a sequence of effects: a slow posterior positivity, a transient anterior negativity, and a transient posterior negativity, respectively. These effects are discussed in relation to functionally distinct parsing mechanisms. They show that ERPs may help to disentangle functionally distinct processes during language comprehension even when no behavioral output is generated by the participant. (C) 1998 Academic Press.