A talk with psychology researcher Matthew Hornsey about political polarization and the psychology behind it. Other topics discussed include: why people can believe such different (and unreasonable) ideas; persuasive tactics; the importance of people criticizing their own group; why groups mainly listen to in-group members and ignore the same ideas from out-group members. 

To learn more about the show, go to behavior-podcast.com. I'm on Twitter at @apokerplayer. See a summary of my work.