(Eleanor J. Gibson)
I admit to one more basic assumption, about language in general this time. The psychological basis of language is abstraction. It is not just emiting sounds in a given sequence, but a conceptual ability of one or many kinds that makes language possible.
I think abstraction is accompanied in perceptual learning by a kind of opposite process of filtering. The invariant relations are abstracted and enhanced, as neurologists have suggested for auditory acuity [von Békésy 1967] by an inhibitionay process of filtering out what is irrelevant. William James spoke of abstraction as a process of "dissociation by varying concomitants."
One thing should be said about the phonological system, even in this abbreviated account. What the child learns is not a mere collection of items of information about sounds at different levels of structure. He learns, rather, a phonological rule system. In his native language, whatever it is, certain sounds may precede and follow others. Some combinations, on the other hand, are not permissible. There are typical consonant clusters that can begin a word, and typical ones that can end it.
Although acquisition of the phonological system is as yet poorly understood, acquisition of the semantic properties of language is a still greater mystery and a matter for psychological dispute. (...) Psychologists have made little progress in the study of meaning. But we know that every child acquires a lexicon - a vocabulary of the words of his language.
The third aspect of speech is its syntactic rule structure. Words from the lexicon are not strung together hit or miss, but in an agreed-upon order. The function of syntactic rules is often said to be that of linking conceptual structures with the phonological representation of them [Langacker 1967]. In any case, the syntactical rule structure is a complex one, specifying the sequential arrangement of units, types of units, and their hierarchical arrangement.