ABSTRACT
In some interactions the two participants each behave similarly, while in others the behaviour of each differs from, but complements, that of the other. Similarity or complementarity 1 in behaviour could be based on similarity or complementarity in personal characteristics. A considerable amount of research has been concerned with assessing the importance, for interpersonal attraction or for the growth or stability of relationships, of similarity on the one hand and complementarity on the other. Not surprisingly, neither is ubiquitously important: the important issue, therefore, is to try to specify which is important where.
