The author calls attention to a basic split between perception and cognition that psychologists or linguists tend to make either explicitly or implicitly. There is some psychological evidence to substantiate, at least for higher developmental levels, the functional importance of this split. The chief problems for psycholinguistics which arise out of it are: how to know when to resist the pressure toward isomorphic descriptions of aspects of language which lie at different places relative to perception/cognition, and how to deal with the relation between development in both kinds of operations and the nature of language development. The author discusses current views and concludes with a list of references. (AMM)