The critical period hypothesis is one of the reasons that some adults are hesitant to take on learning their heritage language. The theory essentially argues that there's a biological window where language learning is the most automatic, somewhere between the age of 2 and puberty. This theory has entered our popular consciousness as a rule that you can't learn a second-language fluently when you're older. However, scientists disagree with this notion because although it will take more conscious effort, it is still possible to become fluent in another language past the "critical window." Specifically, second language acquisition becomes more difficult with age because it requires rewiring your brain to break certain habits that relate to language learning. For example, pronunciation and accent requires breaking habits related to the way you move your mouth to speak, making it more difficult to have native-level pronunciation as you grow older. Beyond neuroscience, though, research has shown that other factors, such as exposure and education influence language learning.

Beginning with Gangnam Style, followed by the success of K-pop groups such as BTS, interest in Korean popular culture has skyrocketed in the past decade. One way this has manifested is through a steep rise in individuals learning the Korean language. According to a study conducted by the Modern Language Association, U.S. college student enrollment in Korean language classes has risen 78% from 2009 to 2016, reaching 15,000, while total enrollment in language classes has plateaued in recent years. The only other widely learned language with significant growth in the span was American Sign Language, which increased enrollments by 37%. Despite this trend, East Asian Studies departments have struggled to accommodate the increasing demand for Korean classes. This is because Korean language classes have been historically limited and under-resourced due to the fact that language programs in East Asian Studies have traditionally focused on Mandarin and Japanese. Experts say that K-pop is the main reason for this trend, coupled with the success of several Korean TV shows and films such as Parasite and Squid Game. The current growing trend of interest in the Korean language and culture has also been an opportunity for South Korea to engage Americans in a variety of other sectors relating to the country including business, politics, economics, and history.