In this paper we reviewed the studies of the relationship between early language and cognitive development. There seem to be two major types of hypothesis. One is cognitive hypotesis, and the other is correlational hypothesis. Cognitive hypothesis suggests that the development of specific cognitive factors is sufficient to account for the child's ability to learn language, and cognitive prerequiste precedes the acquisition of its corresponding linguistic skill. Bates, E. and colleagues, representative of correlational hypotesis, have argued "local homology" model which suggests that there are correlations only at points in development where different behaviors share "specific" structures.
Evidences from the study of the emergence of intentional communicative signals, first words and syntax have been reviewed. The findings from these studies have lent some support to the correlational hypothesis for cognition and language acquisition.
Some proposals for the early language intervention programs were made on the basis of the findings of the studies about the relationship between early language and cognitive development.