What if Chomsky were right?

The outcome of scientific research depends on how a phenomenon is viewed and how the questions are phrased. This applies also to the nativist view of language acquisition. As a complement to MacWhinney’s discussion of nativism from the viewpoint of cognitive psychology, I would like to devote this commentary to the question of the title from the viewpoint of computational linguistics. Formally, the nativist approach has been based on a distinction between finite and infinite sets. Chomsky defines a language as an infinite set of strings (sequence of word forms) and a grammar as a filter which picks the grammatically correct strings from the free monoid1 over the finite lexicon of the language. Language acquisition is described in terms of a language acquisition device (LAD) which has the task of selecting from the infinite set of possible grammars the one which is correct for the language in question. The ‘logical problem of language acquisition’ is how the LAD can select a grammar which is correct for an infinite language, even though the data presented to the LAD (observed sentences) are necessarily finite. This problem is only made worse by Chomsky’s alleged degeneracy of input and poverty of negative evidence, focussed on by MacWhinney. Given that humans can obviously learn language anyway, something in addition to a finite set of data is required. According to Chomsky, it is some innate universal grammar, common to all languages. Differences between languages are attributed to different parameter settings of the universal grammar. As empirical proof for the existence of a universal grammar we are offered language structures claimed to be learned error-free. They are explained as belonging to that part of the universal grammar which is independent from languagedependent parameter setting. Structures claimed to involve error-free learning include