At the end of most years, I’m typically asked to write about the best psychology papers of the past twelve months. This year, though, is not your typical year. And so, instead of the usual “best of,” I’ve decided to create a list of classic psychology papers and findings that can explain not just the rise of Donald Trump in the U.S. but also the rising polarization and extremism that seem to have permeated the world. To do this, I solicited the opinion of many leading psychologists, asking them to nominate a paper or two, with a brief explanation for their choice. (Then I nominated some stories myself.) And so, as 2016 draws to a close, here’s a partial collection of the insights that psychology can bring to bear on what the year has brought about, arranged in chronological order.