The document discusses research on the effects of age on second language achievement and acquisition. Studies have found that learners who begin learning a second language as children tend to achieve higher levels of proficiency and more native-like pronunciation compared to those who begin as adolescents or adults. However, formal learning environments may not provide enough exposure and practice for younger learners' age advantage to emerge. The research also suggests that while age may have a minimal effect on the process of grammar acquisition, it can have a more significant impact on pronunciation development.