Stephen J. Dubner hosts an episode full of the world's most renowned behavior change experts, including Colin Camerer, Ayelet Fishbach, David Laibson, Max Bazerman, Katy Milkman, and Kevin Volpp. Angela Duckworth (psychologist and author of Grit) is our special guest co-host, with Mike Maughan (head of global insights at Qualtrics) as real-time fact-checker.

A language invented in the 19th century, and meant to be universal, it never really caught on. So why does a group of Esperantists from around the world gather once a year to celebrate their bond?