Putnam’s survey was able to distinguish two different kinds of social capital: bridging capital refers to trust between groups, between people who have different values and identities, while bonding capital refers to trust within groups. Putnam found that diversity reduced both kinds of social capital. Here’s his conclusion: Diversity seems to trigger not in-group/out-group division, but anomie or social isolation. In colloquial language, people living in ethnically diverse settings appear to “hunker down”—that is, to pull in like a turtle.
