The main purpose of this paper is to subject to a sociolinguistic quantitative-based treatment some data of variable plural marking in predicate NPs and APs extracted from a sample of spoken language collected in the region of São José do Rio Preto. A more specific aim is to examine whether the best explanation for variable marking of plural can be based on either exclusively formal or exclusively functional constraints, or perhaps based on the interaction between both of them, which would consist in truly competing motivations (DU BOIS, 1985). The results show that neither functional nor formal motivations alone rule the phenomenon, which happens to be strongly constrained by a specific external factor: education level. That is why the most likely explanation for plural marking in predicates is that there are competing motivations, which is a term used by Du Bois (1985), and plural markings are the "limited means", for which multiple forces, the formal or internal and the functional or external motivations, compete among themselves.
Functionalism; Formalism; Plurality; Nominal agreement; Predicate
