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The present theory of friendship is based on a conception of self that regards a central motive to be the person's concern for the well-being and worth of the entity (s) he identifies as self. This concern manifests itself in tendencies to affirm one's sense of individuality, affirm one's more important self-attributes, evaluate one's self positively, and change toward positive self-growth. Friendship involves investments of self in a relationship characterized by the partners' voluntary interdependence and personalized concern for one another. The investment, entailing expenditures of time, personal resources, and personalized concern yields dividends experienced concretely as a partner's self-affirmation value, ego support value, stimulation value, or utility value. Several facets of friendship growth and change are considered, including the degree to which the relationship is difficult to maintain.
Paul H. Wright (Wed,) studied this question.