Learning a second language as an adult can be hard — but it's not impossible

Published May 13, 2025 at 9:02 AM EDT

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 shortwave@npr.org — we'd love to hear from you!

Listen to Short Wave on Spotify, Apple Podcasts and Google Podcasts.

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.

This episode was produced by Thomas Lu, edited by Viet Le and fact-checked by Indi Khera. Alex Drewenskus was the audio engineer.

Special thanks to sociolinguist Amelia Tseng, Fluent City, Dennis Yeuh-Ye Li, Megan Arias, and the Kwong family, especially Christopher, Timothy, Linda and Amanda Kwong.