Washington ? Black couples are more likely than other groups to share core religious beliefs and pray together in the home — factors that have been linked to greater happiness in marriages and relationships, according to a study released Tuesday.

In what was described as the first major look at relationship quality and religion across racial and ethnic lines, researchers reported a significant link overall between relationship satisfaction and religious factors for whites, Hispanics and blacks. The study appears in the August issue of the Journal of Marriage and Family.

True to the old aphorism, couples that pray together stay together, said study co-author W. Bradford Wilcox, director of the National Marriage Project, based at University of Virginia, and “African American couples are more likely to have a shared spiritual identity as a couple.”

The study found that 40 percent of blacks in marriages and live-in relationships attended religious services regularly and had a partner who did the same, compared with 29 percent of non-Hispanic whites and 29 percent of Hispanics.

White couples, in general, reported greater relationship satisfaction than other groups, presumably because of income and education differences, the study said. But the racial gap lessens when religious similarities come into the mix.

“What this study suggests is that religion is one of the key factors narrowing the racial divide in relationship quality in the United States,” Wilcox said.

The strongest difference-maker for couples was spiritual activities such as praying or reading the Bible. “Praying together as a couple is something that is very intimate for people who are religious,” Wilcox said. “It adds another level of closeness to a relationship.”

Still, the study showed religion did not have positive effects for all.

When one partner attends services regularly and the other one does not, relationship satisfaction is lower.

Two nonreligious partners are more content, the study found.

“When couples do things together — whether it’s bird-watching, playing tennis or attending church — they tend to do better,” Wilcox said, and “when they don’t share these activities — particularly when they are important — couples are more likely to suffer.”

The results are based on a new analysis of a 2006 nationwide survey of 1,387 adults ages 18 to 59. Nearly 90 percent were married and the others were cohabiting.