Becoming fluent in a second language is difficult. But for adults, is it impossible? Short Wave hosts Maddie Sofia and Emily Kwong dissect the "critical period hypothesis," a theory which linguists have been debating for decades — with the help of Sarah Frances Phillips), a Ph.D. student in the linguistics department at New York University. You can watch a related video about Emily learning Mandarin here). It's part of the Where We Come From series).Learn more about sponsor message choices: podcastchoices.com/adchoices)NPR Privacy Policy)