A Computational Model of First Language Acquisition

In a recent survey of early language acquisition, Gleitman, Gleitman, Landau, and Wanner (1988) cite Leonard Bloomfield (1933, p. 29) as remarking that "language learning is doubtless the greatest intellectual feat any one of us is ever required to perform." Given this, it is equally no small feat to attempt to build a computer model that does the same thing. Satake's book is one of but a handful of attempts in the computational linguistics tradition to take up this challengemsomewhat surprising given the vast range of linguistic and psychological literature on the subject. Perhaps it is because linguists and psychologists can try to digest just one piece of the acquisition puzzle, while a computational model must typically try to gobble a major chunk of language acquisition whole, or risk being called a mere toy. In this light, Satake should be congratulated for trying to present, in one brief volume, a computational model that attempts to handle facts about morpheme acquisition and intonation; varying word order across languages; verb subcategorization; and classic rule overgeneralization, while at the same time at least paying some attention to what psychologists know about child language. One then obviously runs the risk of stretching too thin, and in fact the volume under review runs far too short in large type. Readers looking for answers to these rich subjects mentioned just above will come away disappointed by a sketch that ultimately can only approximate what computer modeling did in this area more than ten years ago (work by Anderson 1977; Selfridge 1981; and Berwick 1979, 1985). The book exercises the model with a very limited range of sample sentences--just nine examples, with no recursion. More unfortunately, given the emphasis on free word order, no Japanese examples are included. The first quarter of the book is devoted to a rather thin outline of some of the basic psychological results on input available to the child and learnability theory, while the remainder is devoted to the three components of (sub)category generalization, a case analysis of the system working on the examples and a short study of over-regularization, and the use of teacher correction in a so-called "production mode" to repair mistakes. This last point is quite important, for Satake's intended novel contribution to this older literature is stated clearly at the outset: to build an empiricist model of acquisition that is cognitively faithful--that is, one where the structure of language is "out there" in the world and formed by inductive generalization, special properties of parental input (motherese), the order of examples (including negative examples), and the like rather than "in there"--the child's head. Satake means this of course as the polar opposite of "innate" acquisition procedures, which assume a richly structured knowledge of language to begin with. (Satake labels these as "passive" acquisition models