An ERP study of plural attraction in attachment ambiguity resolution: Evidence for retrieval interference

• ERPs were recorded while people read temporarily ambiguous relative clause sentences.
• Plural attractor nouns interfered with agreement processing in both high and low attachment structures.
• Interference effects were revealed by an increased frontal negativity.
• Plural attraction effects may arise from retrieval interference in grammatical sentences.

The memory retrieval processes involved in subject–verb agreement processing in sentence comprehension were examined by recording event-related brain potentials (ERPs) while people read temporarily ambiguous relative clause structures such as The reporter shocked the advisor(s) of the politician(s) who was/were at the meeting. When the relative clause verb was singular, forcing attachment to whichever of the nouns was also singular, the presence of a nearby plural attractor noun created greater interference in the process of retrieving the verb's subject from the memory representation of the sentence so far, revealed by an increased frontal negativity when the attractor noun was plural compared to when it was singular. Crucially, attraction effects did not interact with attachment type. The data suggest that plural attraction effects may arise from retrieval interference in grammatical sentences. The data also suggest that interference from plural attractor nouns in agreement processing is just another instance of the retrieval interference effects that arise whenever it becomes necessary to search the memory representation of a sentence so far to form dependency relationships among the words in the sentence.