Overgeneralizations, competition, and recovery: solving the logical problem with positive evidence.

It would seem to be incomplete for any introduction to language acquisition to leave the ‘logical problem of language acquisition’ untouched – in fact, it would seem to be logical to just start the introduction with the logical problem. MacWhinney lays out a proposal here that attempts to dismantle the logical structure of the logical problem: there is no logical problem, if we consider carefully (a) the actual input that children receive from parents, and (b) the mechanisms that children use to handle possible pitfalls in extracting grammar from the input. The central argument in MacWhinney’s emergentist proposal is that children can learn language by the use of positive evidence without direct negative evidence (perhaps with some indirect negative evidence). Although many connectionists and empirically minded researchers think that positive evidence is all that is needed, the thesis that language acquisition can succeed with just positive evidence would sound like a behaviorist renaissance to most generative linguists. However, MacWhinney provides a detailed list of psycholinguistic mechanisms, explained and situated within the modern dynamical systems theory that he calls ‘emergentism’ (MacWhinney, 1999). Of particular interest among these mechanisms is the competition principle, whichMacWhinney believes is the core to the recovery of overgeneralizations. In other words, when coupled with a few simple fine-tuning devices, competition solves the ‘no negative evidence’ problem. MacWhinney’s newly formulated competition principle is convincing: the competition between episodic support and analogic pressure drives language production to the correct form, which eventually eliminates the incorrect form. Overgeneralization errors that do not receive sufficient auditory support gradually give way to the correct forms that accumulate episodic support over time. For example, because unbuild is rarely heard in the input, the child eventually retreats to the correct forms such as dismantle or knock down. The competition mechanism would work equally well for morphological and syntactic overgeneralizations, for lexically J. Child Lang. 31 (2004), 931–933. Printed in the United Kingdom f 2004 Cambridge University Press