Another factor that makes long-term relationships different from short-term ones is that they are more complex. When a couple begins to take care of a household together, has children, and perhaps has to care for elderly parents, the requirements of the relationship become correspondingly bigger. As a result of this complexity, the partners in close relationships increasingly turn to each other not only for social support but also for help in coordinating activities, remembering dates and appointments, and accomplishing tasks (Wegner, Erber, & Raymond, 1991). The members of a close relationship are highly interdependent, relying to a great degree on each other to meet their goals.
It takes a long time for partners in a relationship to develop the ability to understand the other person’s needs and to form positive patterns of interdependence in which each person’s needs are adequately met. The social representation of a significant other is a rich, complex, and detailed one because we know and care so much about him or her and because we have spent so much time in his or her company (Andersen & Cole, 1990). Because a lot of energy has been invested in creating the relationship, particularly when the relationship includes children, breaking off the partnership becomes more and more costly with time. After spending a long time with one person, it may also become more and more difficult to imagine ourselves with anyone else.
In relationships in which a positive rapport between the partners is developed and maintained over a period of time, the partners are naturally happy with the relationship and they become committed to it. Commitment refers to the feelings and actions that keep partners working together to maintain the relationship. In comparison with those who are less committed, partners who are more committed to the relationship see their mates as more attractive than others, are less able to imagine themselves with another partner, express less interest in other potential mates, are less aggressive toward each other, and are less likely to break up (Simpson, 1987; Slotter et al., 2011).
Commitment may in some cases lead individuals to stay in relationships that they could leave, even though the costs of remaining in the relationship are very high. On the surface, this seems puzzling because people are expected to attempt to maximize their rewards in relationships and would be expected to leave them if they are not rewarding. But in addition to evaluating the outcomes that one gains from a given relationship, the individual also evaluates the potential costs of moving to another relationship or not having any relationship at all. We might stay in a romantic relationship, even if the benefits of that relationship are not high, because the costs of being in no relationship at all are perceived as even higher. We may also remain in relationships that have become dysfunctional in part because we recognize just how much time and effort we have invested in them over the years. When we choose to stay in situations largely because we feel we have put too much effort in to be able to leave them behind, this is known as the sunk costs bias (Eisenberg, Harvey, Moore, Gazelle, & Pandharipande, 2012). In short, when considering whether to stay or leave, we must consider both the costs and benefits of the current relationship and the costs and benefits of the alternatives to it (Rusbult, Olsen, Davis, & Hannon, 2001).
Although the good news about interdependence and commitment is clear—they help relationships last longer—they also have a potential downside. Breaking up, should it happen, is more difficult in relationships that are interdependent and committed. The closer and more committed a relationship has been, the more devastating a breakup will be.