URBANA, Ill., Jan. 22 (UPI) -- Two U.S. studies dispute the stereotype that couples in same-sex relationships are not as committed as their heterosexual counterparts.

Researchers at the University of Illinois at Urbana-Champaign compared 30 committed gay male and 30 committed lesbian couples with 50 engaged heterosexual couples and 40 older married heterosexual couples, as well as with dating heterosexual couples.

All responded to a questionnaire on how they interacted with one another. The couples were also observed during a laboratory task and were monitored for distress by skin conductance and heart rate.

Lead author Glenn I. Roisman said the same-sex relationships were similar to those of opposite-sex couples -- all had positive views of their relationships but those in the more committed relationships resolved conflict better than the heterosexual dating couples.

In the second study, researchers at the University of Washington, San Diego State University and the University of Vermont tracked 65 male and 138 female same-sex couples with 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 found that same-sex couples were similar to heterosexual couples on most relationship variables, and legalized status of a relationship did not seem to be the overriding factor affecting same-sex relationships.

The findings are reported in the journal Developmental Psychology.