Barely a week after assuming office, President Donald Trump set off a worldwide firestorm when he decided to temporarily ban entry to migrants from seven Muslim-majority countries and refugees from all over the world. In response, many people are looking to the past, to see what history can teach us. But this process can fraught with psychological peril. On today's Hidden Brain, we revisit a specific incident from World War II – the American decision to refuse entry to Jewish refugees aboard the SS St. Louis – and explore how it speaks to the current mood in the United States.