Assess the Critical Period Hypothesis in Second Language Acquisition

The ultimate attainment level of Second Language Acquisition (L2A) contrasts sharply with that of First Language Acquisition (L1A) (Birdsong, 1999, p.1). That is: various success versus universal success (Gleitman & Newport, 1995, p.1). This significant difference between L1A and L2A is explained by the Critical Period Hypothesis (CPH). The CPH states that for language acquisition, either first language (L1) or second language (L2), there is a critical period during which it is possible to achieve the same level as natives (Birdsong, 1999, p.1). Once this period is over, the ability to learn language declines (Johnson & Newport, 1989, p.61). In other words, the ultimate attainment level in L2A is determined to a great extent by the age of first exposure to a L2 (Birdsong & Molis, 2001, p.235).