This is Robert Frank on the costs and benefits of commitment:
When It Comes to a Search for a Spouse, Supply and Demand Is Only the Start, by Robert Frank, Economic Scene , NY Times: The economist’s model of the informal market for marriage partners resembles the standard supply and demand model for ordinary goods.
Such models typically assume that people are rational and narrowly self-interested (the celebrated homo economicus stereotype). ... Numbers on a 1-to-10 scale are sometimes used to represent the implicit value of [a person's] endowment, with higher numbers representing combinations of intelligence, good health, physical attractiveness, earning power and other personal characteristics generally viewed as more desirable.
Each searcher is then assumed to follow the rule, “Marry the best person who will have me,” with the result a mating pattern in which 10s pair with other 10s, 9s with other 9s, and so on. ...
[C]ritics are correct to complain that the economists’ simple account ignores the emotional dimension of close personal relationships. ... Such [complaints] have stimulated many economists to examine the role of emotion in human behavior more closely. And it turns out that economic analysis of a specific commitment problem that arises in searches for partners makes it clear why no rational person would want to marry homo economicus.
To illustrate, consider the practical steps you must take once you decide to settle down. Although you cannot meet and evaluate every potential mate, you ... are drawn to one in particular, and that person happens to feel the same way about you. You both want to move forward and start investing in your relationship. You want to get married, buy a house, have children. Few of these steps make sense, however, unless you expect your relationship to continue for an extended period.
But what if something goes wrong? No matter what your mate’s vision of the ideal partner may be, you know there is someone out there who comes closer to it than you. What if that someone were to show up? Or what if you were to become seriously disabled? If you thought your partner would leave under these circumstances, it might not make sense to marry and have children in the first place.
The marriage contract is one way of attempting to achieve the commitment you desire, just as the lease is a way of solving a similar bilateral commitment problem that landlords and tenants confront... But a formal legal contract simply cannot create the kind of commitment people want in a marriage. ...
A far more secure commitment results if the legal contract is reinforced by emotional bonds. The plain fact is that many relationships are not threatened when a new potential partner who is kinder, wealthier, more charming and better looking comes along. Someone who has become deeply emotionally attached to his or her partner does not want to pursue new opportunities, even ones that, in purely objective terms, may seem more promising.
That is not to say that emotional commitments are fail-safe. Who among us would not experience at least mild concern upon hearing that his wife was having dinner with George Clooney ..., or that her husband was having a drink with Uma Thurman? Yet even imperfect emotional commitments free most couples from such concerns most of the time.
The important point is that even though emotional commitments foreclose potentially valuable opportunities, they also confer important benefits. An emotional commitment to one’s spouse is valuable in the economist’s coldly rational cost-benefit calculus because it promotes investments that both partners want to make. But note the twist. These commitments work best when they deflect people from thinking explicitly about their spousal relationships in cost-benefit terms.
Evidence suggests that people who consciously approach those relationships in such terms are much less satisfied with their marriages than others; and when therapists try to get people to think in cost-benefit terms..., it often seems to backfire. That may just not be the way evolution designed us to think about close personal relationships.