PRINCETON, N.J.--President Donald Trump recently introduced immigration reforms that would prioritize education and employment qualifications over family connections in selecting immigrants and nominated immigration hard-liner Kris Kobach as "immigration czar." The moves, like many by Trump, speak to those who feel threatened by what they perceive as a changing America.

Those insecurities are unwarranted, however. With time, people can adapt to societal diversity and actually benefit from it, according to a study led by researchers at Princeton University and the University of Oxford and recently published in the Proceedings of the National Academy of Sciences (PNAS). Those in power especially set the tone for integrating people into a new society.

"If you give people who are different from you half a chance, they will integrate into society pretty well. It is when you purposefully push them out, or erect barriers against them, that problems are introduced," said Douglas Massey, Henry G. Bryant Professor of Sociology and Public Affairs at Princeton's Woodrow Wilson School of Public and International Affairs. "It's important for our political leaders to set the right tone, so proper integration can occur."

The research team examined 22 years of psychological, sociological, and demographic data from multiple waves of the World Values Survey, the European Social Survey, and the Latino Barometer Survey. Together the three datasets included more than 338,000 respondents interviewed in more than 100 countries.

The investigators combined various measures of life satisfaction, happiness, and health to create a "quality of life index" for respondents to each survey. Then, they examined the association between this index and religious diversity. Unlike ethnicity and race, which aren't always collected in surveys and are often measured using divergent categories, religion is well recorded using comparable categories. "Religion is a convenient way to look at the issue of social diversity," Massey said.

The researchers analyzed the short-term effects of religious diversity on quality of life as perceived by individuals at different points in time, but also assessed the long-term effects of diversity on quality of life in different countries over longer spans of time. Although religious diversity was negatively associated with quality of life among individuals in the short run, it bore no association with the quality of life across countries in the long run, a finding that was confirmed in each dataset.

The European Social Survey not only allowed the researchers to measure religious diversity and quality of life, it also permitted them to assess social trust and intergroup contact. These additional measures allowed the investigators to perform a "mediation analysis" that considered both the direct and indirect effects of religious diversity on quality of life.

They found that over short two-year periods rising religious diversity acted to reduce social trust, and thereby undermined the quality of life. Over a longer twelve-year period, however, diversity led to greater intergroup contact that increased social trust to offset the negative short-term influence of diversity on quality of life.

These findings have important policy implications, especially for immigration reform. Whenever people feel insecure for economic reasons and society is also changing around them, it becomes tempting for politicians to blame immigrants for these feelings of insecurity when this is not really the case. It is up to political leaders to set the right tone and message to counteract distrust in the short term so as to encourage integration in the long run, Massey said.

"When it comes to immigrants, political leaders and others have a choice. They can either mobilize sentiments of fear or cultivate feelings of acceptance. It can be tempting for demagogues to mobilize fears for their own political gain, but this is rarely in the best interests of society" Massey said.

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The paper, "Humans adapt to social diversity over time," was published online in PNAS on May 6. The study was supported by Marie Curie Fellowship (grant no. 627982), the Eunice Kennedy Shriver National Institute of Child Health and Human Development (grant no. 5P2CHD047879) and the Nuffield Foundation Grant (grant no. WEL/43108).