The ideal age to start learning a foreign language is an issue that has been debated by 言語学者 (gengogakusha, linguists) for decades. According to the critical period hypothesis, which was first put forward by Wilder Penfield in 1959, a second language can only be fully mastered by those who begin studying it before reaching 思春期 (shishunki, puberty). Many scholars and language learners have since dismissed this as nonsense, yet it's still a theory that is widely accepted around the world.

Japanese actress Yuho Yamashita — who has appeared in a number of German- and English-language films and dramas, including "Der Alte" ("The Old Man") and "The Forest," alongside Natalie Dormer — believes "there's an element of truth to Penfield's assertion," particularly when it comes to 訛り (namari, accent).

"I think to sound like a native speaker you need to start seriously learning a language before the age of 14," she explains. "I know that I'll never sound perfect in either German or English because I started too late with both. All I can do is work as hard as I can to make my speech in the two languages as clear as possible."