It is not our purpose here to review the psycho- and sociolinguistics of first language development (see for example Bruner, 1981; Hamers and Blanc, 1982; Robinson, 1981a). It is enough to say that, well before school age, normal children develop a well-formed system of language. The ease with which language is developed, in the absence of direct instruction, and in circumstances in which uniformity of support and reinforcement (especially from parents) cannot be assumed, has been a continuing source of inspiration for linguists and others for a very long time. It has, in fact, prompted a revival of Cartesian rationalism in linguistics, which explains the rapidity and the complexity of language learning through brain readiness or "pre-wiring". This is not the only theoretical stance possible, of course. However, whether one accepts Chomskian or Skinnerian explanation (to put the matter at its most simplistic level; see Love, 1981), the debate is not over what the child learns, but how (Wells and Robinson, 1982).