Intervention effects in grammar and language acquisition

Intervention effects have been thoroughly studied in formal syntax in the domain of weak islands. They also have recently been appealed to in the study of language acquisition, to capture certain difficulties that young children manifest in the mastery of some object A'-bar dependencies (relatives, questions, topicalizations). Can one unify such distinct utilizations of the concept of intervention under a single formal locality principle? This paper explores the possibility of a unitary approach by proposing solutions for observed discrepancies between the effects in adults and children, and more generally between the different utilizations of the concept of intervention in recent work on adult grammar and language acquisition. Relativized Minimality (RM) is seen as a formal principle penalizing configurations as a function of the distinctness between target and intervener in local relations, where distinctness is precisely expressed as a grammar-based notion. A unitary system consisting of RM and an explicit distinctness hierarchy is argued to be operative in intervention effects in grammar and language acquisition.