The productive and receptive language functioning of Françoise, our DS subject, was thoroughly examined and found to be normal or close to normal in its phonological and grammatical aspects. It proved more compatible with what can reasonably be expected from a moderately MR person with regard to other language subsystems, such as lexicon, semantics, and pragmatics. Françoise's awareness of aspects of her receptive and productive language (including phonological and grammatical aspects) were extremely limited. Corresponding data available from studies conducted by Curtiss, Yamada, Cromer, Bellugi, and others, were also examined. The empirical evidence clearly supports Chomsky's (1981) proposal according to which computational aspects of language, that is, phonology and syntax, are autonomous components, largely independent from general cognitive abilities, whereas conceptual aspects of language, that is, lexicon, semantics, and pragmatics, are more dependent on cognitive functioning. As established, converging evidence exists in the socalled delay-difference literature on language development in regular mentally handicapped subjects when various aspects of language development are systematically compared with respect to mental age.

The data reported and analyzed concerning language-exceptional MR individuals are strong counterindications for any theory attempting to causally relate advanced phonological and grammatical development to general cognitive variables. In particular, the theoretical suggestions coming from the work of Piaget as to the existence of specific ties between operational development and grammatical development were found wanting in many respects. Another cardinal indication to be dismissed on the basis of the present work is the idea that children, particularly MR children, develop linguistically to the extent that they have been trained and taught.