It doesn't matter how compatible two people are: As long as there are crusty dishes in the sink that need cleaning, there are bound be tensions. What's obvious to anyone who's ever shared a kitchen with another human is now supported by research from the Council of Contemporary Families (CCF). According to a forthcoming study that will be published in Socius, imbalanced dishwashing duties is a major source of dissatisfaction in relationships.

The CCF, a nonprofit that researches modern family dynamics in America, looked at the household duties of low- to moderate-income heterosexual parents between 1992 and 2006. By 2006, women reported that dishwashing was the biggest relationship stressor of any chore. Women who washed the majority of the dishes were less satisfied in their relationships, less satisfied in their sex lives, and more likely to have fights with their partner. Couples that split dishwashing duties equally, on the other hand, were much better off. Doing the dishes with a partner was more satisfying for women than sharing any other household task.

One of the reasons dishwashing is the source of so much conflict in the home is the nature of the task. Some chores may need to be done once or twice a week, but as long as a family eats, there will be dishes in the sink. "The battle over the dishes is constant," Dan Carlson, an assistant professor of sociology at the University of Utah and the study's lead author, tells Mental Floss.

There are sociological factors stoking the fire as well: Dishwashing was once the sole domain of women, but in recent decades it has evolved to become one of the most commonly shared household tasks among heterosexual couples. So when partners today do fall into those old patterns, it can hit a nerve.

"Dishwashing, like the other tasks we examined, is historically very gendered and largely the responsibility of women," Carlson says. "Women who find themselves doing the majority of the dishes are likely to feel deprived compared to their peers, leading to more feelings of inequity and unhappiness."

The study did have some good news for proponents of equality in the home: The percentage of heterosexual parents sharing chores, including cleaning, laundry, cooking, and dishwashing, increased across the board between 1992 and 2006. In that same window, the proportion of men doing the majority of those tasks roughly doubled.

Partners that share household duties are also happier and report higher sexual satisfaction. And though it may not feel especially sexy, washing the dishes together has its own set of benefits for couples, according to Carlson. "Doing the task together is a way for couples to bond and strengthen their relationship through cooperation and communication," he says, "which is why sharing dishes appears to be best for relationship quality, especially for women."