Acquisition without evidence: English infinitives and poverty of stimulus in adult second language acquisition

This article provides a Poverty of Stimulus argument for the participation of a dedicated linguistic module in second language acquisition. We study the second language (L2) acquisition of a subset of English infinitive complements that exhibit the following properties: (a) they present an intricate web of grammatical constraints while (b) they are highly infrequent in corpora, (c) they lack visible features that would make them salient, and (d) they are communicatively superfluous. We report on an experiment testing the knowledge of some infinitival constructions by near-native adult first language (L1) Spanish / L2 English speakers. Learners demonstrated a linguistic system that includes contrasts based on subtle restrictions in the L2, including aspect restrictions in Raising to Object. These results provide evidence that frequency and other cognitive or environmental factors are insufficient to account for the acquisition of the full spectrum of English infinitivals. This leads us to the conclusion that a domain-specific linguistic faculty is required.