The setting is a situation in which the children are given the insufficient tools and therefore it is necessary to lend or give the tools mutually I aimed to investigate the role of mimicry in little children's learning of social activities such as cooperation in attaining their common or respective object, communication by language experessing their demands and wishes, and greeting to express thair thanks ot the others for giving or lending them the tools. In Experiment I, concerning the expression of their wishes by language, the children in the experimental group learned to follow another's example significantly differently from those in the control group. They did not, however, perform the examples which were not inevitably necessary to practice the exercises. In Experiment 2, the children were trained to practice activities which had been unacquired by mimicry. Even those activities which were not acquired in Experiment I were easily attained through a short training time by games. And those learnings proved to be effective for other similar exercises. It was shown that the children in Group L who had not been able perform the social activities in preexperimental tests could be trained more effectively when ther were trained with those in Group H who could already behave so than with others in Group L. The untrained cihldren could also be trained by mimicry when they were trained with the trained ones in the postexperimental tests. And their acquisition of mimicry was maintained even when they were trained with other untrained ones. With these observations we should consider that children can more easily acquire social activities when they are trained in mass where mimicry plays a significant part. And it was shown that trainigs with games make those adquisitions more effective.