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President Donald Trump probably would not have been elected if not for the overwhelming support he enjoyed from evangelical Christians. This continues to puzzle and frustrate his opponents, who ask why they voted for a man whose campaign was largely based on hatred and vilification.

While it's easy to blame tribalism or simple hypocrisy, newly published research suggests religiosity exerts two distinct psychological pulls.

It argues genuine piety can be a catalyst for compassion. But the shared rituals that create a cohesive congregation "may also produce hatred of others"—especially among those who lack deeply felt spiritual beliefs.

"Our data suggest that the social activities which accompany religion drive the hostility towards other groups, rather than the quality of one's belief or the degree of devotion," a research team led by Rod Lynch of the University of Missouri writes in the journal Evolutionary Psychological Science.

Building on research that dates back to the 1960s, Lynch and his colleagues remind us that religious people come in two varieties: true believers, and those who embrace a faith tradition as a way of fulfilling some secular need, such as peace of mind or connection to a community.

"The social activities which accompany religion drive the hostility towards other groups."

This distinction between "intrinsic" and "extrinsic" religiosity was laid out by the influential psychologist Gordon Allport in the 1960s, who reported ethnic prejudice was associated only with the latter. Much later research found this to also be true of homophobia.

Lynch's study, the latest in a long line, featured 163 people living in rural Jamaica. The researchers consider this a good population for examining prejudice formation, since they "share similar socioeconomic and educational backgrounds, and are all from the same mixed race and culture."

To measure intrinsic belief, each participant indicated how strongly they agreed with nine statements, such as "My religious beliefs are really what lie behind my whole approach to life."

Extrinsic beliefs were measured by their responses to nine different assertions, including "What religion offers me most is comfort when sorrows and misfortune strike," and "Occasionally I find it necessary to compromise my religious beliefs in order to protect my social and economic well-being."

Participants also indicated how frequently they prayed, and how often they attended services. To measure hostility to outsiders, they responded to one additional statement: "I blame people of other religions for much of the trouble in the world."

"We found that religious beliefs themselves are positively associated with a willingness to sacrifice for one's beliefs, and a greater tolerance of (outsiders)," the researchers report. However, "the social facets of religion, such as attendance, promote greater hostility" toward people of other faiths.

One specific finding is telling: Frequently attending services (and thereby cementing one's inclusion in the community) was linked to higher levels of bigotry against non-believers, but "devotion to religious principles" was linked to lower levels. It seems a connection with the divine inspires an inclusive outlook.

The results suggest joining together with like-minded others, and using rituals to affirm your bond, can produce a distrust and dislike of outsiders. Actual spiritual devotion negates these prejudicial impulses—but when that's lacking, they can drive one's beliefs and behaviors.

So when it comes to religion and prejudice, it seems the problem is not the genuinely devout, but rather the hangers-on.