Kluge: The Haphazard Construction of the Human Mind

considerable ambiguity in Chomsky’s suggestion. What would it mean for a language to be perfect or optimal? That one could express anything one might wish to say? That language is the most efficient possible means for obtaining what one wants? Or that language was the most logical system for communication anyone could possibly imagine? It’s hard to see how language, as it now stands, can lay claim to such grand credentials. The ambiguity of language, for example, seems unnecessary (as computers have shown), and language works in ways neither logical nor efficient (just think of how much extra effort is often required in order to clarify what our words mean). If language were a perfect vehicle for communication, infinitely efficient and expressive, I don’t think we would so often need “paralinguistic” information, like that provided by gestures, to get our meaning across.

As it turns out, Chomsky actually has something different in mind. He certainly doesn’t think language is a perfect tool for communication; to the contrary, he has argued that it is a mistake to think of language as having evolved “for” the purposes of communication at all. Rather, when Chomsky says that language is nearly optimal, he seems to mean that its formal structure is surprisingly elegant, in the same sense that string theory is. Just as string theorists conjecture that the complexity of physics can be captured by a small set of basic laws, Chomsky has, since the early 1990s, been trying to capture what he sees as the superficial complexity of language with a small set of laws.[33] Building on that idea, Chomsky and his collaborators have gone so far as to suggest that language might be a kind of “optimal solution… [to] the problem of linking the sensory-motor and conceptual-intentional systems” (or, roughly, connecting sound and meaning). They suggest that language, despite its obvious complexity, might have required only a single evolutionary advance beyond our inheritance from ancestral primates, namely, the introduction of a device known as “recursion.”

Recursion is a way of building larger structures out of smaller structures. Like mathematics, language is a potentially infinite system. Just as you can always make a number bigger by adding one (a trillion plus one, a googleplex plus one, and so forth), you can always make a sentence longer by adding a new clause. My favorite example comes from Maxwell Smart on the old Mel Brooks TV show Get Smart: “Would you believe that I know that you know that I know that you know where the bomb is hidden?” Each additional clause requires another round of recursion.

There’s no doubt that recursion — or something like it — is central to human language. The fact that we can put together one small bit of structure (the man) with another (who went up the hill) to form a more complex bit of structure (the man who went up the hill) allows us to create arbitrarily complex sentences with terrific precision (The man with the gun is the man who went up the hill, not the man who drove the getaway car). Chomsky and his colleagues even have suggested that recursion might be “the only uniquely human component of the faculty of language.”

A number of scholars have been highly critical of that radical idea. Steven Pinker and the linguist Ray Jackendoff have argued that recursion might actually be found in other aspects of the mind (such as the process by which we recognize complex objects as being composed of recognizable subparts). The primatologist David Premack, meanwhile, has suggested that although recursion is a hallmark of human language, it is scarcely the only thing separating human language from other forms of communication. As Premack has noted, it’s not as if chimpanzees can speak an otherwise humanlike language that lacks recursion (which might consist of language minus complexities such as embedded clauses). [34] I’d like to go even further, though, and take what we’ve learned about the nature of evolution and humans to turn the whole argument on its head.

The sticking point is what linguists call syntactic trees, diagrams like this:

<…>

Small elements can be combined to form larger elements, which in turn can be combined into still larger elements. There’s no problem in principle with building such things — computers use trees, for example, in representing the directory, or “folder” structures, on a hard drive.

But, as we have seen time and again, what is natural for computers isn’t always natural for the human brain: building a tree would require a precision in memory that humans just don’t appear to have. Building a tree structure with postal-code memory is trivial, something that the world’s computer programmers do many times a day. But building a tree structure out of contextual memory is a totally different story, a kluge that kind of works and kind of doesn’t.

Working with simple sentences, we’re usually fine, but our capacity to understand sentences can easily be compromised. Take, for example, this short sentence I mentioned in the opening chapter:

People people left left.

Here’s a slightly easier variant:

Farmers monkeys fear slept.

Four words each, but enough to boggle most people’s mind. Yet both sentences are perfectly grammatical. The first means that some set of people who were abandoned by a second group of people themselves departed; the second one means, roughly, “There is a set of farmers that the monkeys fear, and that set of farmers slept; the farmers that the monkeys were afraid of slept.” These kinds of sentences — known in the trade as “center embeddings” (because they bury one clause directly in the middle of another) — are difficult, I submit, precisely because evolution never stumbled on proper tree structure.[35]

Here’s the thing: in order to interpret sentences like these and fully represent recursion (another classic is The rat the cat the mouse chased bit died), we would need to keep track of each noun and each verb, and at the same time hold in mind the connections between them and the clauses they form. Which is just what grammatical trees are supposed to do.

The trouble is, to do that would require an exact memory for the structures and words that have just been said (or read). And that’s something our postal-code-free memories just aren’t set up to do. If I were to read this book aloud and suddenly, without notice, stop and ask you to repeat the last sentence you heard — you probably couldn’t. You’d likely remember the gist of what I had said, but the exact wording would almost surely elude you.[36]

As a result, efforts to keep track of the structure of sentences becomes a bit like efforts to reconstruct the chronology of a long-ago sequence of events: clumsy, unreliable, but better than nothing. Consider, for example, a sentence like It was the banker that praised the barber that alienated his wife that climbed the mountain. Now, quick: was the mountain climbed by the banker, the barber, or his wife? A computer- based parser would have no trouble answering this question; each noun and each verb would be slotted into its proper place in a tree. But many human listeners end up confused. Lacking any hint of memory organized by location, the best we can do is approximate trees, clumsily kluging them together out of contextual memory. If we receive enough distinctive clues, it’s not a problem, but when the individual components of sentences are similar enough to confuse, the whole edifice comes tumbling down.

Perhaps the biggest problem with grammar is not the trouble we have in constructing trees, but the trouble we have in producing sentences that are certain to be parsed as we intend them to be. Since our sentences are clear to us, we assume they are clear to our listeners. But often they’re not; as engineers discovered when they started trying to build machines to understand language, a significant fraction of what we say is quietly ambiguous.[37]

Take, for example, this seemingly benign sentence: Put the block in the box on the table. An ordinary sentence, but it can actually mean two things: a request to put a particular block that happens to be in a box onto the table, or a request to take some block and put it into a particular box that happens to be on the table. Add another clause, and we wind up with four possibilities:

Put the block [(in the box on the table) in the kitchen].

Put the block [in the box (on the table in the kitchen)].

Put [the block (in the box) on the table] in the kitchen.

Put (the block in the box) (on the table in the kitchen).