第二言語習得に適した年齢はありますか？
The issue of age was first addressed with the critical period hypothesis. The strict version of this hypothesis states that there is a cut-off age at about 12, after which learners lose the ability to fully learn a language. However, the exact age marking the end of the critical period is debated, and ranges from age 6 to 13, with many arguing that it is around the onset of puberty. This strict version has since been rejected for second-language acquisition, as some adult learners have been observed who reach native-like levels of pronunciation and general fluency. However, in general, adult learners of a second-language rarely achieve the native-like fluency that children display, despite often progressing faster in the initial stages. This has led to speculation that age is indirectly related to other, more central factors that affect language learning.
6 to 13