Becoming fluent in a second language is difficult. But for adults, is it impossible? Science says no. In this encore episode, Short Wave host Emily Kwong) dissects 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. Together, Emily and former *Short Wave *host Maddie Sofia) explore where the theory comes from, how it applies to second-language acquisition and what it means for Emily's efforts to learn Mandarin Chinese as an adult.*Have a linguistics or neuroscience question? Email us at [email protected]) — we'd love to hear from you!Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave).*Learn more about sponsor message choices: podcastchoices.com/adchoices)NPR Privacy Policy)