Reflections

Straight from the horse's mouth: Chomsky talks

(From Reflections on Language (1975))

"...by studying language we may discover abstract principles that govern its structure and use, principles that are universal by biological necessity and not mere historical accident, that derive from mental characteristics of the species. A human language is a system of remarkable complexity. To come to know a human language would be an extraordinary intellectual achievement for a creature not specifically designed to accomplish this task. A normal child acquires this knowledge on relatively slight exposure and without specific training. He can then quite effortlessly make use of an intricate structure of specific rules and guiding principles to convey his thoughts and feelings to others, arousing in them novel ideas and subtle perceptions and judgments. For the conscious mind, not specially designed for the purpose, it remains a distant goal to reconstruct and comprehend what the child has done intuitively and with minimal effort. Thus language is a mirror of mind in a deep and significant sense. It is a product of human intelligence, created anew in each individual by operations that lie far beyond the reach of will or consciousness."

"We can gain some insight into UG [Universal Grammar], hence LT(H,L) [a theory of how humans learn language], whenever we find properties of language that can reasonably be supposed not to have been learned. To make the discussion more concrete, consider a familiar example, perhaps the simplest one that is not entirely trivial. Think of the process of forming questions in English. Imagine again our neutral scientist, observing a child learning English. Suppose that he discovers that the child has learned to form such questions as those of (A), corresponding to the associated declaratives:

(A) the man is tall---is the man tall?

the book is on the table---is the book on the table?

etc.

Observing these facts, the scientist might arrive at the following tentative hypothesis as to what the child is doing, assuming now that sentences are analyzed into words:

Hypothesis 1: The child processes the declarative sentence from its first word (i.e., from "left to right"), continuing until he reaches the first occurrence of the word "is" (or others like it: "may," "will," etc.); he then preposes this occurrence of "is," producing the corresponding question (with some concomitant modifications of form that need not concern us).

This hypothesis works quite well. It is also extremely simple. The scientist has every right to be satisfied, and will be able to find a great deal of evidence to support his tentative hypothesis. Of course, the hypothesis is false, as we learn from such examples as (B) and (C):

(B) the man who is tall is in the room--is the man who is tall in the room?

Our scientist would discover, surely, that on first presentation with an example such as "the man who is tall is in the room," the child unerringly forms the question (B), not (C) (if he can handle the example at all). Children make many mistakes in language learning, but never mistakes such as exemplified in (C). If the scientist is reasonable, this discovery will surprise him greatly, for it shows that his simple hypothesis 1 is false, and that he must construct a far more complex hypothesis to deal with the facts. The correct hypothesis is the following, ignoring complications that are irrelevant here:

Hypothesis 2: The child analyzes the declarative sentence into abstract phrases; he then locates the first occurrence of "is" (etc.) that follows the first noun phrase; he then preposes this occurrence of "is," forming the corresponding question.

Hypothesis 1 holds that the child is employing a "structure-independent rule"--that is, a rule that involves only analysis into words and the property "earliest" ("left-most") defined on word sequences. Hypothesis 2 holds that the child is employing a "structure-dependent rule," a rule that involves analysis into words and phrases, and the property "earliest" defined on sequences of words analyzed into abstract phrases. The phrases are "abstract" in the sense that neither their boundaries nor their categories (noun phrase, verb phrase, etc.) need be physically marked. Sentences do not appear with brackets, intonation boundaries regularly marking phrases, subscripts identifying the type of phrase, or anything of the sort.

By any reasonable standards, hypothesis 2 is far more complex and "unlikely" than hypothesis 1. The scientist would have to be driven by evidence, such as (B), (C), to postulate hypothesis 2 in place of the simpler and more elementary hypothesis 1. Correspondingly, the scientist must ask why it is that the child unerringly makes use of the structure-dependent rule postulated in hypothesis 2, rather than the simpler structure-independent rule of hypothesis 1. There seems to be no explanation in terms of "communicative efficiency" or similar considerations. It is certainly absurd to argue that children are trained to use the structure-dependent rule, in this case. In fact, the problem never arises in language learning. A person may go through a considerable part of his life without ever facing relevant evidence, but he will have no hesitation in using the structure-dependent rule, even if all of his experience is consistent with hypothesis 1. The only reasonable conclusion is that UG contains the principle that all such rules must be structure-dependent. That is, the child's mind (specifically, its component LT(H,L)) contains the instruction: Construct a structure-dependent rule, ignoring all structure-independent rules. The principle of structure-dependence is not learned, but forms part of the conditions for language learning."