A growing body of evidence shows that same-sex couples have a great deal to teach everyone else about marriage and relationships.
Most studies show surprisingly few differences between committed gay couples and committed straight couples, but the differences that do emerge have shed light on the kinds of conflicts that can endanger any relationship.
The findings offer hope that some of the most vexing problems are not necessarily entrenched in deep-rooted biological differences between men and women. And that, in turn, offers hope that the problems can be solved.
Next week, California will begin issuing marriage licenses to same-sex couples, reigniting the national debate over gay marriage. But researchers say it also presents an opportunity to study the effects of marriage on the quality of all relationships.
"When I look at what's happening in California, I think there's a lot to be learned to explore how human beings relate to one another," said Sondra E. Solomon, an associate professor of psychology at the University of Vermont. "How people care for each other, how they share responsibility, power and authority - those are the key issues in relationships."
The stereotype for same-sex relationships is that they do not last. But that may be due, in large part, to the lack of legal and social recognition given to same-sex couples. Studies of dissolution rates vary widely.
After Vermont legalized same-sex civil unions in 2000, researchers surveyed nearly 1,000 couples, including same-sex couples and their heterosexual married siblings. The focus was on how the relationships were affected by common causes of marital strife like housework, sex and money.
Notably, same-sex relationships, whether between men or women, were far more egalitarian than heterosexual ones.
In heterosexual couples, women did far more of the housework; men were more likely to have the financial responsibility; and men were more likely to initiate sex, while women were more likely to refuse it or to start a conversation about problems in the relationship.
With same-sex couples, of course, none of these dichotomies was possible, and the partners tended to share the burdens far more equally.
While the gay and lesbian couples had about the same rate of conflict as the heterosexual ones, they appeared to have more relationship satisfaction, suggesting that the inequality of opposite-sex relationships can take a toll.
"Heterosexual married women live with a lot of anger about having to do the tasks not only in the house but in the relationship," said Esther D. Rothblum, a professor of women's studies at San Diego State University. "That's very different than what same-sex couples and heterosexual men live with."
Other studies show that what couples argue about is far less important than how they argue. The egalitarian nature of same-sex relationships appears to spill over into how those couples resolve conflict.
One well-known study used mathematical modeling to decipher the interactions between committed gay couples. The results, published in two 2003 articles in The Journal of Homosexuality, showed that when same-sex couples argued, they tended to fight more fairly than heterosexual couples, making fewer verbal attacks and more of an effort to defuse the confrontation.
Controlling and hostile emotional tactics, like belligerence and attempts at being domineering, were less common among gay couples.
Same-sex couples were also less likely to develop an elevated heartbeat and adrenaline surges during arguments. And straight couples were more likely to stay physically agitated after a conflict.
"When they got into these really negative interactions, gay and lesbian couples were able to do things like use humor and affection that enabled them to step back from the ledge and continue to talk about the problem instead of just exploding," said Robert W. Levenson, a professor of psychology at the University of California, Berkeley.
The findings suggest that heterosexual couples need to work harder to seek perspective.
The ability to see the other person's point of view appears to be more automatic in same-sex couples, but research shows that heterosexuals who can relate to their partner's concerns and who are skilled at defusing arguments also have stronger relationships.
One of the most common stereotypes in heterosexual marriages is the "demand-withdraw" interaction, in which the woman tends to be unhappy and to make demands for change, while the man reacts by withdrawing from the conflict.
But some surprising new research shows that same-sex couples also exhibit the pattern, contradicting the notion that the behavior is rooted in gender, according to an abstract presented at the 2006 meeting of the Association for Psychological Science by Sarah R. Holley, a psychology researcher at Berkeley.
Levenson says this is good news for all couples. "Like everybody else, I thought this was male behavior and female behavior, but it's not," he said. "That means there is a lot more hope that you can do something about it."