This essay addresses the question of whether the age at which a second language (L2) is acquired constitutes the only factor which accounts for oral proficiency accuracy in L2. The first part of the essay refers to the preponderance of age over other variables in language acquisition studies, and explains the most referenced theory: the Critical Period Hypothesis; providing evidence in favour and against it. The second section deals with other factors which may be involved on L2 production and perception variability. The relevance of this subject is not only determined by its value for language acquisition research, but also by the implications related to the educational perspective. It is a common view that speaking an L2 with a foreign accent
This does not necessarily apply to particular learners, as it may be the case of foreign language teachers, newscasters, interpreters, singers, actors and actresses, who may be interested in acquiring a native-like accent.

Among the factors which account for proficiency in L2 acquisition, age has been considered the most important one, and therefore, it has been the most researched variable in experiments related to this area of knowledge. Lenneberg’s (1967) influential Critical Period Hypothesis (CPH) claims that there is a cut off period at puberty when acquiring an L2. After this critical period, complete mastery of the language is no longer possible, and for the oral competence in particular, learners will not be able to achieve a native-like accent. This theory is usually grounded on neurological changes such as loss of plasticity in the brain. Researchers reached different conclusions regarding the location of the critical period: 15 years (Patkowski, 1990), 12 years (Scovel, 1988), or even earlier. Long (1990) pointed out that a second language learner would achieve a native-like accent if the onset age is 6 years old, and would always maintain a foreign accent if the language was
An alternative hypothesis is the Sensitive Period Hypothesis (SPH), which advocates the existence of a sensitive period rather than a specific age. One of the first studies on this topic by Asher and García (1969) reflected on the optimal age to learn a second language. The subjects consisted of an experimental group of 71 Cuban immigrants between the ages of seven and nineteen, who had been in United States for five years, and a control group of thirty American children. The task was to read four English sentences which were replayed and judged by nineteen American high school students who had to decide if the speaker had a native pronunciation, near-native pronunciation, slight accent, or definite accent. The results showed that “if