In a scene from the movie "Lincoln," a Democrat arguing against passage of the 13th Amendment derisively mentions the idea of interracial marriage to ridicule the legislation that would abolish slavery.

A century-and-a-half later, as an African-American president is inaugurated for a second term, interracial unions still are relatively rare.

And faith groups may be part of the reason Americans still find it so difficult to transcend race and ethnicity in matters of the heart, new research indicates.

Believers played a major role in the civil rights movement, but the voluntary segregation still found in houses of worship on Sunday mornings appears to limit the likelihood non-Hispanic white Americans will date, much less marry, a black, Hispanic or Asian partner.

In one national study of dating practices, researchers found those who attended church most often were far less likely to have dated someone from another race.

And in a separate study of more than 12,000 people who were or had been married, only Catholics were significantly more likely than people from other traditions to cross significant racial or ethnic boundaries.

"Segregated churches breed segregated lives," says researcher Samuel Perry of the University of Chicago.

Segregated pews

Churches are still one of the least likely places white, black, Asian and Hispanic Americans will encounter one another.

Pew's 2007 American Religious Landscape Survey found non-Hispanic whites made up more than 9 in 10 members of mainline Protestant churches and more than 8 in 10 members of evangelical Protestant churches, while more than 9 in 10 members of historically black churches were non-Hispanic blacks. Nearly 3 in 10 Catholics were Hispanic, compared with just 3 percent of mainline Protestants.

Research finds that being in a church with few or no members of another race makes a difference in choosing romantic partners.

About half of people who attend church once a year or never said they had dated interracially; just 27 percent of respondents who attend weekly or more reported dating a person of another race, according to a study using data from the 2007 Baylor Religion Survey.

Those who attended multiracial churches, however, were more likely to have dated a person of another race, Perry reported at the recent annual meeting of the Society for the Scientific Study of Religion.

He reports similar findings regarding attitudes toward marriages in a forthcoming article on "Religion and whites' attitudes toward interracial marriage with African-Americans, Asians and Latinos" in the Journal for the Scientific Study of Religion. (There are differences of opinion over whether Hispanics should be classified as a racial or ethnic group. The U.S. Census Bureau is considering reclassifying Hispanic as a race rather than an ethnicity.)

It is more than just a matter of churchgoers having less contact with people of other races, according to Perry.

"Just as important, however, is the fact that religious communities develop cultural boundaries that define who is and is not 'like us.' Due to less interaction with mixed-race couples, attendees of more segregated congregations will likely have a narrower vision of what constitutes an 'ideal' romantic match than persons in integrated faith communities," he writes.

Walking the walk

It is not religion in itself that is to blame, the research indicates.

People with no religious affiliation were not statistically more likely to be in intermarriages than evangelical or mainline Protestants or people from other religions, researchers from Baylor University reported at the Society for the Scientific Study of Religion meeting. Joshua Tom and Brandon Martinez analyzed data from more than 12,000 ever-married persons in the 2002 National Survey of Family Growth.

The only exceptions were Catholics. Catholics were almost twice as likely to be in an intermarriage and Catholics who attended services more frequently were slightly more likely to be in an intermarriage, the researchers found.

"The growing Hispanic population probably has a lot to do with it," Tom said. Researchers said Catholics also are more likely to attend the nearest parish than choose a congregation from a larger area to be in a more homogenous group.

In his research, Perry found that whites who more frequently engage in devotional practices such as prayer and reading sacred texts were more likely to interracially date and to be more supportive of interracial marriage.

The relative lack of interracial romance among churchgoers in racially homogenous congregations is "far more about racial segregation" than an inherent defect in faith traditions. "I don't find that at all. In fact, I find the reverse," he said.

Perry's advice to pastors seeking to promote a society where love transcends race includes considering devoting a Sunday or a couple of Sundays to talk about the evils of prejudice. And to ask their flocks: "Are you walking the walk" of building bridges that cross boundaries.

Reflecting on prejudice in our time may be pretty good advice in general.

There is a tendency in watching movies such as "Lincoln" to look back at historical struggles against evil with a sense of moral superiority.

In this awards season, as honors are heaped upon the movie depicting the politicking necessary in the 19th century to produce social change, it may be helpful to consider how far we still have to travel on the journey to equality.

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David Briggs, a national religion writer who holds a master's degree from Yale Divinity School, is executive director of the International Association of Religion Journalists. He wrote this column for the Association of Religion Data Archives.