ABSTRACT
A fundamental substantive distinction that is not sufficiently emphasized in theoretical or applied work in child development and mental retardation is that between cognition and language. Language is another behavioral realm where a competence-performance distinction has been the subject of intensive research. Linguistic competence refers to a key postulate in Chomsky's theory; that children utilize an inborn biologically based capacity for language to sample their language environment and to construct a generative grammar of the language. A Skinnerian formulation of language acquisition in terms of mands and tacts would dismiss the competence-performance distinction entirely. The conception of cognition and language as the same thing is very popular among lay people and prevalent among behavioral scientists and educators. From a phylogenetic point of view, the major difference between man and dumb animals is linguistic behavior, hence the tendency to equate language with reasoning.
