Closeness and Interpersonal Outcomes in Same-Sex Friendships: An Improvement of the Investment Model and Explanation of Closeness

In this article I have tried to improve the investment model. The investment model suggests that human relationships are maintained by the outcome of friendships, by the outcome with people other than one's friends, and by the investment in one's friends. In an analysis of same-sex friendships among college students (N=414), the concept of equity theory was added to the investment model. When considering such feelings as anger and guilt, which are not included in the investment model, it turned out that satisfaction with relationships greatly influences commitment. In other words, whether relationships last or not depends on satisfaction. Therefore, the concept of the investment model is enough to explain commitment. The investment model was looked at using a covariance structure analysis. This was accomplished by manipulating the variables in the model: replacing the interpersonal outcome with one's own outcome or the outcome of the other person. An analysis was also made by looking at various degrees of closeness. The results show that the lower the degree of closeness, the more one thinks of the outcome of other people. As relationships deepened, a sense of guilt and all the social exchange variables except anger increased. The effect of investment (the giving of time or gifts) was minimal and in the case of women, tended to decrease commitment or result in a break of relationships. When investment was removed from the investment model, the model tended to fit better.