Deriving the Complementarity Effect: Relativized minimality in Breton agreement

Abstract Breton φ-agreement is characterized by the Complementarity Effect , which allows pro -dropped but not lexical DPs to control φ-agreement. We contrast verbal and prepositional systems: a lexical DP co-occurs with the root form of a preposition, but with a 3rd.sg. ( frozen agreement ) form of a verb. We argue that frozen agreement arises through φ-relativized locality: the Breton v P independently shows nominal properties, and thus intervenes for agreement. The φ-probe of T Agrees with the v P for 3rd.sg. rather than the v P-internal subject. In the prepositional system on the other hand, lexical DPs occur with bare stems and φ-inflection spells out affixed pronouns. The mechanics predict that in verbal constructions where the subject originates outside the v P, it is local enough to control the agreement of T, which correctly yields Have under a prepositional analysis as the sole verb immune to the Complementarity Effect. Finally, we propose a typology of Complementarity Effects in agreement depending on the interaction of intervention (frozen agreement) and syntactic incorporation past the intervener.