The human brain did not evolve rules that shape language grammatically; instead, grammar rules evolved to fit the brain. This reversal from the ordinary expectation is proposed in a forthcoming article in Behavioral and Brain Sciences titled “Language as Shaped by the Brain,” by two psychologists, Morten H. Christiansen and Nick Chater. (Various drafts are circulating on the web. Here is one.) This theory changes a central question for this blog. The old question asked what changes to the brain occurred to permit syntactic constructions? Was that change some kind of adaptation or a spandrel? Did it just permit recursion or did it do more? The new approach puts all those questions aside and raises new ones.
The Christiansen and Chater paper addresses one of the deep mysteries of human development: the speed with which children start talking. Nobody doubts that children pick up the words from those they hear spoken around them, but the grammar comes with suspicious ease. Children are able to create sentences they have never heard. The standard explanation for the past 50 years has been that children are born with an understanding of grammar, but an alternate proposal is that language has evolved to be easy to learn. The idea is that if you start with a language that has no syntax, one will evolve. One speaker might say red saw I hat and another says red hat saw I but after a few generations the form that is easiest to say and understand will be the standard and new speakers will find that the language is more easily learned. The relationships expressed come from a pre-existing general intelligence rather than from a specialized syntactic module.
The change marks a break with the nativist philosophical tradition revived by Chomsky, but does not return to the "blank slate" philosophy that nativisim replaced. At least, it does not embrace the naĩve form of the old blank slaters. In that tradition, people were said to be born with a mind as blank as a new blackboard and anything could be written on it. The Christiansen and Chater account denies that there are any innate ideas already written in the mind, but some things can be marked down much more easily than others. The brain has a geometry—i.e., various traits and limitations that make it easy or hard to write something on it. In the case of modern languages that have a long history of passage from generation to generation, any language an infant must learn is so well adapted to the brain's geometry that it is picked up without any serious difficulty.
The dimensions of this mental geometry include:
Perception: The limitations of attention and memory "may ... force a code that can be interpreted incrementally rather than [by using one of] the many practical codes in engineering in which information is stored in large blocks." On this blog (and not in the Christiansen/Chater paper) I treat language as a pilot of attention. That task, of course, forces incremental communications [attend to X... attend to Y...].
Motor: "The basic phonentic inventory is transparently related to deployment of the vocal apparatus." In other words, the sounds we use are obviously dependent on the sounds we can make. Our use of a stream of air to form words forces a sequential construction of messages. Thus, perception and motor ability work together to shape a language that will express itself serially, either by using a fixed word order or by a fixed order of suffixes or prefixes.
Thought processing: Planning and motor control "involve the extraction and further processing of discrete elements occurring in complex temporal sequences." Language is not just one word after another. For example (I'm supplying the example; Christian and Chater are not so strong on examples) in tool-making a person may be performing one step in anticipation of a final product. Similarly, a speaker may utter a phrase in anticipation of the whole sentence.
Pragmatic processes: Pragmatics concerns the difference between the literal interpretation of words and the way they are understood. Take a sentence like John arrived and began to sing. That can only be interpreted as meaning John began to sing. We can, however, imagine a language that includes a rule stating that whenever a subject is omitted the first person singular is to be understood. In that case the full sentence would be John arrived and I began to sing. But no language has this imaginary rule and nobody has to be taught that the omitted subject in the second half of the sentence is John. Even very small children understand the sentence correctly without having to be explicitly taught this rule. The old theory was that the rule for understanding the meaning of this anaphoristic sentence must be built into the child from birth, and indeed the rule does have to be specifically programmed into a computer if you want it to use language correctly. The Christiansen/Chater paper says that the understanding comes from the pragmatic working of the brain and does not require a special linguistic module. Many of the rules that seem particularly arbitrary to students of formal linguistic rules, are of this type and, say Christiansen and Chater, may refelect pragmatic constraints (dimensions).
Generative grammar does not include these dimensions, so some other kind of grammar must take its place. Christiansen and Chater support "the 'lexical turn' in linguistics, focusing on specific lexical items [i.e., words] with their associated syntactic and semantic information." (This argument was anticipated at the Barcelona meeting; see: Words Are More Human than Syntax.) "Specifically, we adopt a Construction Grammar view of language, proposing that individual constructions consisting of words or combinations thereof are among the basic units of selection." Construction Grammar is an approach that focuses on words and stereotypical units like spic-and-span rather than syntactic categories like noun phrases. It studies language on a much less abstract level than generative approaches.
The idea of a "basic unit selection" is essential to the Christiansen/Chater paper and plays no role at all in generative accounts of language origins. The idea that language evolved is taken literally by Christiansen and Chater.
- Words and set phrases play the role of genes, the units that are selected.
- Languages are the equivalent of species.
- An idiolect (the speech of an individual) is the product of its constructions, just as an individual organism is the product of its genes.
- A language is a set of mutually intelligible idiolects, just as a species is a set of mutually interbreeding individuals.
- In biological evolution, species evolve according to their environmental fitness. In linguistic evolution, languages evolve according to their adaptation to the mental geometry of speakers.
Although the idea is similar to Terrence Deacon's notion of the co-evolution of brain and language, it is not the same because it sees evolution in one direction only. Language adapts to the brain; brain and language do not adapt to each other. Deacon proposes a mechanism known as the Baldwin effect, by which learned behavior can enter the genetic code. But Christiansen and Chater have run simulations that calculate the Baldwin effect does not work if language is evolving more rapidly than the species.
The idea is also different from Richard Dawkins' idea of memes or the "genes" of culture. Christiansen and Chater say of meme-theorists, "[Their] explanations of fashions (e.g., wearing baseball caps backwards), catchphrases, memorable tunes, engineering methods, cultural conventions and institutions (e.g., marriage, revenge killings), scientific and artistic ideas, religious views, and so on, seem patently to be products of sighted watchmakers; i.e., they are products, in part at least, of many generations of intelligent designers, imitators, and critics." In the Christiansen/Chater theory of how the brain shapes language, the process is unconscious and undirected. The structure emerges without conscious intervention.
The paper's limitation is that it lists dimensions, but does not show how they work. It is not an achievement of the first level that puts all questions behind it, but then we cannot really expect or demand the kind of Einstein mastercoup that says: here are the dimensions, here is the geometry, and here is the formula for drawing a line across the map. What we have instead is a tentative list of dimensions, a vague sense of how the geometry works, and no formula at all for predicting the results. What we need now are a number of Galileos who can work out the rules of movement through this mental space.
More next week.