Nowak, M. A., Plotkin, J. B. & Jansen, V. A.
The evolution of syntactic communication
Nature 404 (2000): 495.

Press release

Evolution : Speaking in syntactical tongues
HENRY GEE

Ireneo Funes - ‘Funes the Memorious’ - is perhaps the most memorable character in the remarkable fiction of the late, great Argentine essayist Jorge Luis Borges. Hit on the head in a riding accident, the teenage Funes has perfect recall. Far from conferring on him the attributes of a superman, Funes is literally crippled by memory. Because he recalls everything in perfect detail, he is unable to sort memories into categories.

For example, Funes cannot conceive of the abstract category ‘dog’ into which he could slot his neighbour’s beagle, the Labrador down the road, and so on. Each instance becomes a category to itself. Funes’ memory curses him with a syntax-free view of the world. So rich in detail, it is effectively meaningless.

For, as Martin Nowak of the Institute for Advanced Study in Princeton, New Jersey, and colleagues now show, the invention of syntax allowed us to evolve a complex language. Human language is ‘syntactical’ in that it is made of discrete segments, arranged in particular ways to make meaningful sentences.

Animal communication, Nowak and colleagues explain in Nature1 , is believed to be ‘non-syntactical’. Each utterance (or ‘word’) refers to a specific event. For example, ‘Lhooq!’ might mean ‘Watch out! There is a green-eyed yellow jaguar slinking around in the dappled shade underneath the jacaranda tree across the stream’.

Funes’s world was non-syntactical: he needed a separate way of describing a labrador from a beagle, and even separate words for describing beagles seen at dawn rather than dusk, or beagles seen sideways, upside down, while barking, and so on. All because he could not refer each example to an abstract category - ‘dog’- for all occasions, that could be suitably modified by separate, abstract parts of speech such as adjectives and verbs.

Human language, on the other hand, is clearly syntactic. Rather than summarizing events or scenarios into single words, each of which must be memorized separately, we memorize the individual operators (nouns, verbs and so on) that make up scenarios, and use grammatical rules to combine these separate elements into meaningful sentences. There are two distinct advantages to this, and one disadvantage.

First, non-syntactical language does not travel well. In a non-syntactical society, it would be hard to explain the meaning of ‘Lhooq!’ to somebody who wasn’t there at the time. But abstract categories such as ‘jaguar’ and ‘slinking’ can be learned separately, without direct experience of the object referred.

Second, the modular nature of syntactical language means that people can shuffle words to create entirely imaginary, synthetic experiences - summarizing concepts that have never been directly experienced. Syntactical language is therefore much more flexible than non-syntactical forms of communication. Non-syntactical language is hamstrung by new experience. In the sentence above about jaguars and jacarandas, it is easy to substitute ‘alligator’ for ‘jaguar’ if the species of predator happens to vary. But in non-syntactical language, this would mean creating an entirely new word, different from ‘Lhooq!’

The disadvantage of syntax is that it implies grammar: rules for arranging words. And these rules must be learned, because not every arrangement makes sense.

Nowak and colleagues do not demonstrate this with the kind of vague arm-waving that has given evolutionary psychology a bad name. Rather, they discuss the relative merits of syntactical and non-syntactical language by building a mathematical model in which the advantages and disadvantages of the two forms of communication are expressed in terms of equations. The model reveals that the advantages of syntactical communication are clear, but only become evident in situations in which the need to describe complex events outweighs the significant cost of learning abstract words and grammatical rules for creating sentences.

In other words, our ancestors only invented language in the sense we understand it today once they found themselves in interesting, varied environments in which flexible, modular communication had advantages for survival.