Harvard political scientist Robert Putnam, famous for Bowling Alone, was displeased to find the downside of diversity:
The results of his new study come from a survey Putnam directed among residents in 41 US communities, including Boston. Residents were sorted into the four principal categories used by the US Census: black, white, Hispanic, and Asian. They were asked how much they trusted their neighbors and those of each racial category, and questioned about a long list of civic attitudes and practices, including their views on local government, their involvement in community projects, and their friendships. What emerged in more diverse communities was a bleak picture of civic desolation, affecting everything from political engagement to the state of social ties.
[...]
But even after statistically taking [all other factors] into account, the connection remained strong: Higher diversity meant lower social capital. In his findings, Putnam writes that those in more diverse communities tend to “distrust their neighbors, regardless of the color of their skin, to withdraw even from close friends, to expect the worst from their community and its leaders, to volunteer less, give less to charity and work on community projects less often, to register to vote less, to agitate for social reform more but have less faith that they can actually make a difference, and to huddle unhappily in front of the television.”“People living in ethnically diverse settings appear to ‘hunker down’ — that is, to pull in like a turtle,” Putnam writes.
In documenting that hunkering down, Putnam challenged the two dominant schools of thought on ethnic and racial diversity, the “contact” theory and the “conflict” theory. Under the contact theory, more time spent with those of other backgrounds leads to greater understanding and harmony between groups. Under the conflict theory, that proximity produces tension and discord.
Putnam’s findings reject both theories. In more diverse communities, he says, there were neither great bonds formed across group lines nor heightened ethnic tensions, but a general civic malaise. And in perhaps the most surprising result of all, levels of trust were not only lower between groups in more diverse settings, but even among members of the same group.
“Diversity, at least in the short run,” he writes, “seems to bring out the turtle in all of us.”