When we “bridge differences” in schools, we are working toward fostering positive intergroup relationships, whether those bridges are between students, teachers, school leaders, parents/caregivers, or people in our communities.

Differences don’t necessarily need to divide people, but we do have a tendency, rooted in evolution, to split the world into “us” and “them”—and to treat members of our own “ingroup” with kindness while behaving badly toward outside groups. These tendencies can be especially pronounced at times when we feel stressed or threatened, anxious about our own security or survival.

Through mental shortcuts known as “heuristics,” we often make snap judgments about other people—which can turn negative in certain circumstances. For instance, opinions about immigrants might be formed by negative stories on cable news, which tap into the “availability heuristic,” wherein we make our judgments based on immediately accessible or repetitious information, e.g., “immigrants will overthrow everything we love about America.” People who aren’t exposed to other information will start to form stereotypes about immigrant groups, which in some cases can be used to rationalize exploitation or discrimination. These kinds of psychological processes make it easier for us to demonize outgroups and engage in chauvinistic behavior, helping create the divides we live in today.

Why does social and political polarization seem to be getting worse in American society?

This is a topic of fierce debate among political scientists and sociologists. We know that rapid demographic changes are introducing much more diversity to our neighborhoods, workplaces, government, and culture. This is leading to more anxiety among formerly dominant demographic groups, which elicits the kinds of psychological judgments and biases described above. When those biases go unchecked, feelings of anxiety can lead to antagonism and prejudice. These divisions are now driving decisions about where Americans live, whom we befriend, and how we’re educating our children—serving to divide us further.

But Americans want to live in a country where our political differences don’t have to push us apart. A recent NBC News/Wall Street Journal survey found one topic of agreement between Americans of different parties polled: 80 percent of respondents agreed that the country is “divided,” while 90 percent of those surveyed believed that the divisions between Democrats and Republicans are a “serious problem.”

By understanding the social and psychological roots of polarization, we can promote solutions that help bring people together by sharing commonalities, not just differences.