Abstract: On the basis of the results of our longitudinal and experimental researches upon language development of 12 children from birth to three years of age,this article analyzed and compared the stages of the child's language and cognitive development, the respective influencing factors, investigating the relationship between the child's development of language and cognition(thought).Four viewpoints on this question are derived:(1) In the stage of the child's concrete thought before 1 year of age (pre-linguistic stage),children do have cognition (not only sensory perception,memory and presentation, but also thought),but have no language.This showed clearly that it is invalid to say that all the thoughts are linked with language.Nevertheless,abstract thought characteristic to mankind are closely and indivisibly linked with language.Having highly generalized language,human beings can possess highly abstract thoughts.(2) Development of cognition (thought) is the basis of language development.This is illustrated and proved from three aspects,i.e.the order of grasping parts of speech,the process of acquiring personal pronouns,and the effects of cognitive development on language development.(3) Thus we can see that the relationships between development of cognition (thought)and that of language are two-way,dialectic and interacting complicatedly.It is inappropriate to say the relationship between cognition(thought)and language is one determining the other.(4) Approaching the origin of both cognition(thought)and language,we should adopt a dialectical materialist point of view.The reason why human beings have language and highly generalized abstract thoughts is that they practise for the need of adapting,reflecting and changing the objective world.Lastly,brief comments are made on Whorf′s and Piaget's relevant views.

Key words: language development, development of cognition(thought), role of language, cognitive basis, practical activities