"Among the committed couples, there were very few differences that we were able to identify either in terms of how satisfied these couples were, how effectively they interacted with one another or how their bodies responded physiologically while they were interacting with one another," Glenn I. Roisman, of the University of Illinois at Urbana-Champagne, said in an interview.

He and his colleagues compared 30 gay male and 30 lesbian couples with 50 engaged heterosexual couples, 40 older, married heterosexual couples and dating heterosexual couples.

They found that regardless of sexual orientation, as the level of commitment increased, so did the ability to resolve conflict; debunking the myth that same-sex relationships are not built on the same level of commitment as heterosexual ones.

In the second study researchers, who focused on how legal status affected relationship quality, followed 65 male and 138 female same-sex couples in civil unions, 23 male and 61 female same-sex couples not in civil unions and 55 heterosexual married couples over a three-year period.

The researchers from the University of Washington, San Diego State University and the University of Vermont found that same-sex couples, regardless of their legal status, were more satisfied with their relationships and reported more positive feelings toward their partners and less conflict than heterosexual married couples.

But gay and lesbian couples not in civil unions were more likely than same-sex couples in civil unions, or heterosexuals who were married, to end their relationships, according to the study.

Both studies were published in the journal Developmental Psychology.

"My personal view is that I think it's very hard to make the case as has been made that these same-sex relationships are fundamentally different from opposite-sex relationships in the presence of data like these and other data in the developmental literature," said Roisman.

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