The Marked Effect of Number on Subject–Verb Agreement

English speakers distinguish between one entity and more than one entity in virtually every utterance they produce. The distinction is present in the morphology of most nouns as well as in the basic grammatical dependency of subject–verb agreement. Three experiments employing a sentence production task explored the nature of the representation that underlies singular and plural count nouns in English and how that representation interacts with the processes that implement agreement during production. The results provide evidence that singular count nouns are unmarked or lack a grammatical feature for number while plural count nouns are marked or possess a feature. This asymmetry in markedness contributes to the greater incidence of plural agreement errors relative to singular errors observed in naturally occurring and experimentally elicited errors. In particular, the evidence suggests that agreement with singular count nouns is implemented by a default process whereas agreement with plural count nouns is implemented on the basis of unambiguous number information.