Much attention has been devoted by sociologists and social psychologists to the question of the introduction of new members into a group or society. Preoccupation with this broad problem is visible, for instance, in studies of conversion to a religion, of movement from one social class to another, and of change of residence from one community or country to another. Not all studies, however, deal with the same aspects of the problem. Some focus on the factors which bring about such movement from one group to another. Others are concerned with the effects the movement has on both the group of origin and the group of destination. Finally, a good proportion of the studies purport to answer the following questions: What changes occur in the basic values, sentiments, and ways of behaving of the individual? To what extent are there such changes, and through what processes do they take place? This latter group of studies centres on concepts such as acculturation, integration, assimilation, adaptation, or absorption.
These concepts all refer to the same phenomenon, although perhaps from different angles. Park and Burgess, for instance, present the following general notion of “assimilation”: “A process of interpenetration and fusion in which persons and groups acquire the memories, sentiments, and attitudes of other persons or groups, and by sharing their experience and history, are incorporated with them in a common cultural life.” Blau has a very similar conception of the integration of the socially mobile into a new class. So does Eisenstadt with the concept of “adaptation,” although his definition is stated in terms of the final result rather than in terms of the process whereby it is achieved.