One distinctive strength of male couples is that their tendency to candidly discuss respective preferences extends to sexuality as well, including choices that may startle some heterosexuals. For example, while the extent of non-monogamy in gay-male partnerships is often exaggerated, openly non-monogamous relationships are more common than among lesbians or heterosexuals. Many gay couples work out detailed agreements about what kinds of sexual contact are permissible outside the relationship, under what circumstances and how often.

Notably, however, while the dating relationships of male couples are less stable than those of female-female or male-female couples, their formalized unions are as stable as those of heterosexuals and more stable than formalized female-female unions.

The sociologist Virginia Rutter, a co-author of “The Gender of Sexuality,” argues that heterosexual couples might reach a deeper level of intimacy and avoid destructive meltdowns in their relationships if they also discussed their sexual desires and ambivalences more frankly.

Still, same-sex marriages too are affected by the gender expectations that pervade our society, and in perhaps surprising ways. Gay and lesbian individuals have internalized many of these expectations, even if they have rejected or modified some of the constraints those expectations impose. This makes same-sex couples more likely to share priorities and habits.

Women, for instance, have long been socialized to believe that providing and receiving emotional support is a routine obligation in partnerships, something that, like putting food on the table, must be done every day. The University of Texas sociologist Debra Umberson says that women tend to be “all in” when it comes to anticipating, reading and responding to their partner’s emotional and physical needs.

“But this plays out very differently when a woman is in a relationship with another woman compared to one with a man,” Professor Umberson said in an interview. “With two women, there is a lot of reciprocity in care work — with each spouse aware of the other’s needs and preferences, and responding actively to those.” In heterosexual marriages, however, husbands “tend to take care work for granted, are often unaware of the care work their wife provides and commonly fail to recognize her needs for emotional support.”

Gay-male couples also exhibit reciprocity in care work, though at a lower level of intensity than women. Like heterosexual men, gay partners typically value preserving emotional autonomy and independence over breaking down boundaries in pursuit of greater intimacy. Gay men, said Professor Umberson, are more “low-key” than women, offering emotional and instrumental care to a partner when it is clearly needed, instead of treating it as a routine obligation. And gay men tend not to expect such care unless they explicitly ask for it.