There is much debate over the timing of the critical period with respect to SLA, with estimates ranging between 2 and 13 years of age. These estimates tend to vary depending on what component of the language learning process a researcher considers. For instance, if an SLA researcher is studying L2 development, they will likely conclude that the critical period ends at around age 3. If another SLA researcher is studying L2 development, they may conclude that the critical period ends at a much later age. These differences in research focus are what create the critical period timing debate.
Cases of deaf and feral children provide evidence for a biologically determined CP for L1. Feral children are those not exposed to language in infancy/childhood due to being brought up in the wild, in isolation and/or confinement. A classic example is , a victim of who was deprived of social interaction from birth until discovered aged thirteen. Her father had judged her retarded at birth and had chosen to isolate her. She was kept strapped to a potty chair and forced to wear diapers. She was completely without language. Her case presented an ideal opportunity to test the theory that a nurturing environment could somehow make up for the total lack of language past the age of 12. After seven years of rehabilitation Genie still lacked linguistic competence, although the degree to which she acquired language is disputed. Another case is ‘Isabelle’, who was incarcerated with her deaf-mute mother until the age of six and a half (pre-pubescent). She also had no language skills, but, unlike Genie, quickly acquired normal language abilities through systematic specialist training.
If so, lateralization cannot be the evidence of the critical period.
The critical period hypothesis states that the first few years of life is the crucial time in which an individual can acquire a if presented with adequate stimuli. If language input does not occur until after this time, the individual will never achieve a full command of language—especially .
Case Study of Genie - Critical Period Hypothesis
It is commonly believed that children are better suited to learning a second language than are adults. However, general second-language research has failed to support the critical period hypothesis in its strong form (i.e., the claim that full language acquisition is impossible beyond a certain age). According to Linda M. Espinosa, especially in the United States the number of children growing up with a home language that is not English but Spanish is constantly increasing. Therefore these children have to learn the English language before kindergarten as a second language. It is better for young children to maintain both their home language and their second language. Cultivating their home language, children create their own cultural identity and become aware of their roots. This fact leads to the question whether having the ability to speak two languages helps or harms young children. Research shows that the acquisition of a second language in early childhood confers several advantages, especially a greater awareness of linguistic structures. Furthermore it is advantageous for young children to grow up bilingually because they do not need to be taught systematically but learn languages intuitively. How fast a child can learn a language depends on several personal factors, such as interest and motivation, and their learning environment. Communication should be facilitated rather than forcing a child to learn a language with strict rules. Education in early childhood can lead to an effective educational achievement for children from various cultural environments.
Evidence for and against the Critical Period Hypothesis …
B. Harley also measured eventual attainment and found the two age groups made similar mistakes in syntax and lexical selection, often confusing French with the L1. The general conclusion from these investigations is that different aged learners acquire the various aspects of language with varying difficulty. Some variation in grammatical performance is attributed to maturation, however, all participants began immersion programs before puberty and so were too young for a strong critical period hypothesis to be directly tested.