Critical Period in Language Learning

It is believed that the teenager and an adult will find much more difficult in learning a new language than they first learned about their first language as a child. many linguists believe it is because of critical period of a language development. the critical period is a theory that explains why it is easy for children to learn languages that an adult.
what exactly is a critical period....?
the idea of a critical period comes from the study of animals. we say that that there is a critical period the only time when the animal can learn a new skill. the critical period starts in the first week or month of an animal life. during this time its brain is ready to learn new things. however when the animal gets older the critical period ends, it cannot learn anymore. so, there are skills must be learned when the animal is young. if not, they cannot learn them as a adult.

Now, let us consider the critical period for leaning languages in the human. as you probably notice children learn new languages much more easily and quickly than an adult. one theory that there is a critical period from language learning, the theory is that people brain change when they are adolescence. and this changes make it more difficult for adults to learn a new language than for children. It can be concluded that there is a critical period from both animals and humans can learn certain things.