A little  healthy debate at work is essential, since different viewpoints can encourage people to defend and improve the rationale behind their decisions and to see other potential options. But if that debate starts to slip into a clear "us versus them" split, you've got a problem.

People tend to polarize for a few psychological reasons:

First, they want to fit in. As outlined in uncertainty-identity theory and discussed by psychologists such as Michael A. Hogg and Janice Adelman, people are motivated to reduce as much uncertainty about their lives and identity as they can. One way to do this is to identity with and become involved in a group.

People also take sides so they can start to do and say what the others in the group do for approval and acceptance. This can be particularly problematic when, because of poor, fear-based leadership or culture, individuals see adhering to the group standard as essential to being selected for projects, promotions or other benefits that they personally equate with success or stability.

Heated feelings also comes from being around people with the same views, as it reaffirms a position. As Rob Henderson discusses in an article for Psychology Today, psychologists such as Serge Moscovici and Marisa Zavalloni have shown that beliefs strengthen when we see them reflected back at us. At the same time, people tend to associate popularity with "right" or "good" in a moral or ethical sense. So the more people do or say something, the more normal it seems and the more likely people are to see themselves as also having permission to do or say it.

People want to be accepted by their target group, but at the same time, they also have a need to feel special and unique. So once they are part of a group, they personally can take the ideologies or behaviors of that group to a just slightly more visible extreme. This more extreme behavior then serves as a new model for others in the group, who can try to match it. Over time, this heightened extremism causes the rift between groups to widen.

Plus, as Robert Kovach notes in his article for Harvard Business Review, the need to meet specific needs in specific markets can cause unintentional siloing, where each silo has its own goals. This can cause conflicts over initiatives or wasteful duplication of efforts across the organization.

All that said, here are a few things you can do to bring people together:

1. Point out not only how an individual has contributed to the group vision, but how they've done so in unique ways.

This satisfies the need for inclusion and acceptance while also helping the worker have a sense of individuality.

2. Present fair opportunities to all.

Inviting individuals from all levels to participate in activities, being transparent about advancement requirements or other expectations, providing one-on-one time where people can voice concerns or goals, and establishing policies to prevent bias in selection all can help your team feel like conformity isn't a requirement for advancement.

3. Get people moving and collaborating.

Try trading workers from the offices you have, sending people to conferences, emphasizing how each department contributes to larger goals, and using technology to bridge geographical difficulties.

You also can choose projects that require cross-department work throughout rather than stage-based handoffs, shadowing, choosing specific office configurations, introducing people, and cross-department mentoring programs to effectively help people break down silos and broaden worker perspectives.

4. Surprise and inform.

Unexpected events or opportunities can break monotony and shake people out of group habits they might be tempted to develop. Randomly offering balanced, objective information about many topics further may show workers that it's okay to have opinions or safe behaviors that might go against the grain.

5. Shut down bullying before it breeds.

Whether you see workers mocking someone else's ideas or purposely leaving others out of the loop, don't tolerate mistreatment, as it quickly can make the office environment and culture completely toxic. Be clear about the kind of behavior you want to see and reward people when they deliver it.

Polarization is rampant in business and beyond, but these strategies are just the start--there's plenty more you can do as a leader to handle polarizing people or situations and unify your company. The bottom line, though, is that that unity is a choice. Let people see you make that choice consistently every day and they'll be more prompted to choose it.