One of the principal tenets of innovation is that diverse groups have better ideas. And the opposite holds true: like-minded people have come up with such great ideas as the Edsel, thalidomide, launching the Challenger, the German invasion of the Soviet Union, the Bay of Pigs, and the Iraq war.

The perils of groupthink, according to Cass Sunstein’s new book, Going to Extremes, apply equally well to business and politics. The more polarized the groups, the less they listen to other ideas, which in turn leads to even more polarized groups who don’t listen…well, you see where this is going.  And just as Fox News viewers will hear no evil about their preferred politicians, people in different divisions of a single company will stubbornly resist giving up their cherished ways of doing business while rejecting good ideas that come from other divisions.  The more closely people identify with their groups, in fact, the less they are open to anyone else’s ideas.

This could explain the stunningly low success rate of mergers and  acquisitions. It also explains why it is absolutely necessary to get diverse people in the room when you need any organizational change. When working with those people, however, you will be more successful if you remind them of the things they have in common: the MSNBC and Fox viewers could be sports fans, and your different divisions could be coping with the same tough economy.

Of course, finding those commonalities takes work, both from leaders and group participants. And diverse groups take a little more time to create better ideas. Ultimately, though, the extra time and effort are worth it—unless you’d like to be famous for one of your industry’s most famous disasters.