Chomsky's hypothesis was that the inborn linguistic capacity of humans is sensitive to just those rules that occur in human languages—and in no other sorts of language or system. In other words, something quite specific to language has evolved in the human brain, something that enables the steady stream of language sounds to be perceived by the infant as distinct in an important way from other sounds and that also enables the infant to begin to break down the flow of this stream into meaningful parts, arranged, as the infant somehow recognizes, in a systematic way. Chomsky likened this capacity to the capacity to walk, in the sense that it is a behavior in which humans naturally engage, without the need for special instruction, as soon as they are developmentally ready—provided the environment permits. That is, walking proceeds if the toddler has undergone maturation sufficient for growth of bones and muscles, and language development occurs if the environment provides exposure to language. Both are part of our biological endowment. It is thus no accident that there are many similarities among languages: The many systems, or grammars, that underlie them are ultimately generated by the human brain.
That there are as many different grammars as there are languages is evident. But linguists cannot discover the grammar of any one of them without careful study of the actual language as it is spoken. At the outset one might propose any number of possible grammars to account for the speech heard in a given language. How many sets of rules might one be able to think up that would generate the things people say? Think for a moment about how many explanations one might propose for how a machine—say, a car—works, in the absence of actually looking inside to see the components and what drives their operation. One might come up with many explanations, ranging from "There are forty little guys in there pedaling for all they're worth" to very complicated schemes for having one element move another, which would then move another. . . something like a Rube Goldberg contraption. Someone might even hit on the correct explanation, and we who actually know how the car works know that there is only one correct explanation.
So it is with language. There are many possible grammars that would serve to produce a given language. But if we adults cannot peer inside the mechanism and learn which is the correct one, how on earth does a small child find it on his or her own? Even if we are willing to assume, with Chomsky, that what the child brings to bear is an innate capacity to project the right grammar on the language spoken in the environment, we might not wish to endow—to overburden—this child with all the grammars to select from that would be necessary for all languages. But if babies do not know in advance which language they will be confronted with at birth, how else could they possibly find the right grammar?
The hypothesis proposed to answer this question is that despite their surface differences all human languages share a fundamental structure, and what is common to them all has come to be known as universal grammar. Innate in all of us, according to this hypothesis, is the ability to apply this universal grammar to whatever languages we are faced with at birth. This explanation is not universally accepted; some have maintained, for example, that the human capacity for language is not richly specified in the brain but is rather a special function of the general cognitive abilities humans possess.
Chomsky's early hypotheses regarding the nature of the human linguistic capacity date from the mid-1950s. During the next 20 years or so, researchers following that line of thinking worked with the kind of explanation discussed earlier in this chapter—that is, that each of us is endowed with an innate capacity to respond to rules of language of the sort I have described. But there are so many languages, and each has its own set of rules. How is it possible for a brain to possess innately a system adequate to the task?
The approach then taken by Chomsky and others was to attempt to "factor out" general principles that hold for all languages, principles that govern application of the rules of languages. Under this new principles and parameters formulation, which crystallized around 1980, it is these that constitute the universal grammar. Variation in languages results from the ways in which these principles apply. There is a finite set of ways in which the principles may apply; these are the parameters (Chomsky, 1995). The parameters have been likened to a set of switches, each having a fixed range of potential settings. The actual language the learner is exposed to provides the data that trigger the setting of the switches. Under the principles and parameters hypothesis, learning the syntax of one's first language is a matter of setting these switches; acquiring language is a process of fixing the parameters in one of the permissible ways. With no requirement that the innate component specify all manner of language-specific rules of the sort described previously, the hypothesized innate machinery of language can be reduced.
Whichever way one looks at it, some of the questions we find ourselves asking regarding the language capacity of humans are:
How is language organized in the brain?
How does it work?
If a person speaks more than one language, how are these languages stored?
Once the rules of a given language have been internalized by the child, how
and where are they represented in the brain?
We cannot take the direct path and look inside for the answers, because even when the brain is exposed to view for medical reasons, as in Penfield's work, one sees neither rules such as VP → V (NP) (PP*) nor principles and parameters lurking there in some recognizable form. But the recently developed sophisticated methods of scanning the brain, as we saw in the preceding chapter, allow us to observe brain activity during the performance of language-related tasks, among others. Nonetheless, we see no rule hopping about the cortex clamoring to be recognized.
There are, however, experiments that do provide us with information. Brain-damaged patients can serve as subjects of such experiments (Damasio & Tranel, 1993). These experiments indicate that certain brain structures link areas of knowledge about traits, sounds, and movements of birds, for example, with the nouns and verbs associated with them. Subjects in the experiments could describe, using verbs, what was taking place in pictures of activities involving birds, but did much worse than non-brain-damaged controls in using the appropriate nouns, such as duck, ostrich, and other bird names. Another conclusion to be drawn, according to the experimenters, is that areas of the brain that handle nouns are not the same as those that handle verbs.
In the next chapter we will turn to the sorts of experiments that have been carried out in recent attempts to understand the acquisition and functioning of language in our species.