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Cats, dogs, people

And  compositionality

What makes the faculty of human language different from any non-human system of communication is that it is ‘compositional’ – in almost all respects composed of parts which can be put together in organised, ordered ways, like the parts of a face.

The only exceptions are laughter, gestures like waving goodbye, swearing and cursing, gestures made with the mouth like tut tut, and a small handful of expressions like shh, argh, wow, expressing reactions to and feelings about people and events, exclusively part of discourse. Even these forms are almost exculisively built from elements of the sound structure of the language, and often integrated into overly grammatical structures in significant ways.

Other than these special cases, the words, the way they are put together in what is known as syntax, the sounds they are built from with an ordering in time between the gestures, their meanings, are all structured. This makes the faculty of human language quite different from the barks of dogs and the miaows of cats, or the songs, squawks, and tweets of birds, or the clicks and songs of dolphins and whales, or even the elaborate systems of chimpanzees.

There are corresponding physical and semantic features in the sign languages of the deaf.

The structure of language allows humans to use a finite number of symbols, the sounds or ‘phonemes‘ of the language or the signs of a signed language, to say an infinite number of things and be understand by any other native speaker or signer. This is known as ‘discrete infinity’.

No non-human has ever shown evidence of anything like discrete infinity. To this extent, humans are both unique and exceptional in the animal kingdom. But for some reason, the exceptionality of human language is strongly resisted by some.

Some geneticists take this line because of the difficulty of identifying the corresponding sequence in the DNA. But to me, the onus is on those who deny any sort of genomic explanation to provide a more plausible explanation of discrete infinity.

This is not to suggest that children are born knowing how to talk, a self-evidently absurd aunt sally sometimes peddled by those opposed to any idea of human exceptionality or specific genetic endowment. The claim is just that children come to the task of learning language as though expecting to find structures which make discrete infinity definable.  Exactly how this happens has been at the centre of linguistic research for the past 60 years. It is the main focus of the proposal here.

The linguist, Stephen Anderson, sets out the issues here in his excellent and famous 2004 book, Doctor Dolittle’s delusion.


When babies babble, they sometimes seem to be experimenting with the phonotactics and phonetic features of a given target language. But there is no evidence of meaning here.

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