Brain Development and Learning a Second Languages

Although adults can achieve a high level of competence in the grammar and vocabulary of second languages, they are generally less successful in mastering its pronunciation. Research studies have supported the claim that adults can rarely acquire native-speaker pronunciation in a second language. The critical period theory explains that why adult learners cannot master native-like pronunciation in second languages. This theory states that ability to acquire native-speaker pronunciation disappears around the age of twelve, when, after lateralization, language functions permanently settle in the left hemisphere of the brain. Evidence from aphasia patients confirms that most language is processed in the left hemisphere of the brain. Evidence from the brain surgery patients shows that lateralization causes the brain to lose some of its earlier capacity to acquire language. That is why adults cannot acquire native-speaker pronunciation in a second languages may be unattainable, adults should not stop trying to improve their languages pronunciation.