Surface cues and robust inference as a basis for the early acquisition of subcategorization frames

How could children possibly acquire their first subcategorization frames? The hypothesis that they directly observe the syntactic structures of the utterances they hear raises two questions. First, how can children parse input utterances reliably without already knowing the syntactic properties of all the words in them? Second, how do children survive the ungrammatical or misconstrued utterances they inevitably encounter? This paper suggests a specific inference algorithm that substantially reduces the effects of ungrammatical or misconstrued input. Since children must have some such inference procedure, they can use approximate cues to determine syntactic structure. In particular, they can use string-local surface cues rather than global constraints. Such cues make it possible to discover relevant syntactic structure in an utterance without already knowing all the words in it. This paper suggests a possible set of cues for English subcategorization frames that assumes only the ability to detect the ends of utterances and knowledge of a few function morphemes and proper names. Simulation experiments on naturally occuring, child-directed English show that these cues, combined with the proposed inference mechanism, do surprisingly well at discovering subcategorization frames.