DAVID GREENE, HOST:
From Syria to Afghanistan, to Russia and Ukraine, the United States finds itself confronting some major foreign policy challenges. There are old rivalries and new one testing the limits of the United States.
NPR social science correspondent Shankar Vedantam regularly joins us to talk about matters related to individual and organizational behavior, but today, he's found some new research that's relevant to the way we think about foreign conflicts and he's in our studios. Shankar, welcome back.