Summarize Written Text

Researchers studying adult second-language acquisition have increasingly questioned the long-held assumption that a strict critical period, ending around puberty, determines whether near-native fluency is achievable. Earlier studies, often based on immigrants who began learning a new language at varying ages, appeared to show a sharp decline in ultimate attainment for those who started after adolescence, lending support to a biologically fixed cutoff. More recent work, however, has identified adult learners who reach fluency indistinguishable from native speakers on a range of grammatical and phonological measures, suggesting that age alone cannot fully explain the variation in outcomes. Researchers now point to a cluster of interacting factors that better predict success: the intensity and consistency of exposure, the degree of similarity between the learner's native language and the target language, motivation and identity-related investment in the new linguistic community, and the availability of corrective feedback during practice. Of these, structured feedback has emerged as particularly influential, since learners who receive immediate, specific correction of pronunciation and grammatical errors tend to plateau at noticeably higher proficiency levels than those who receive only general encouragement or no feedback at all. This has practical implications for language education, suggesting that adult classrooms should prioritize high-frequency, low-stakes speaking practice paired with targeted correction over passive grammar instruction, which tends to build explicit knowledge without transferring effectively into spontaneous fluent use. Some researchers caution against overstating these findings, noting that certain aspects of phonological perception, particularly the ability to distinguish sounds absent from one's native language, do appear to become measurably harder to acquire after early childhood, even among highly motivated and well-instructed adult learners. The current consensus therefore treats the critical period not as an absolute barrier but as a gradient of diminishing ease, with some linguistic subsystems remaining more age-sensitive than others.