New research suggests that "religious homogamy" -- a phenomenon where people tend to date and marry others who share their religious beliefs -- is partially a result of inferences about religious people's personalities.

Researchers at New Zealand's University of Otago measured how religious and non-religious individuals perceive the "openness"-- a primary dimension of personality associated with intellectual curiosity--of potential religious and non-religious mates. They found that non-religious participants in particular associated religious behavior with less openness, and that this inference led them to devalue religious individuals as romantic partners.

In the first study, religious and non-religious participants decided whether or not they would date forty possible romantic partners who varied in how frequently they attended religious services. The research team discovered that non-religious participants found potential partners less desirable, and also less open to new experience, as their religious behavior increased.

In a second study, participants judged potential partners who attended religious services frequently or infrequently, some of whom also disclosed that they were open to new experiences (with statements such as "I don't pretend my ethical perspective is the only one"). Non-religious participants preferred non-religious partners, and also those who were open to new experiences, while religious participants showed the opposite preferences. What's more, the same-religiosity bias was reduced when a partner revealed he or she was open to experience.

The findings suggested that religious and non-religious participants evaluate the same "open" behaviors differently. That is, there was agreement that non-religious individuals are relatively open-minded, but not on whether being open-minded is a good thing.

Professor Jamin Halberstadt, one of the study's authors, said that the experiments provide insight into one possible personality mechanism behind religious in-group dating bias.

"They illustrate, for the first time, that people's decision to partner with religious or non-religious individuals can be determined by personality traits that religiosity is believed -- rightly or wrongly -- to predict, rather than religion itself," he said.

The findings are detailed in the international journal Social Psychological and Personality Science.