Many people have watched the movie “Tarzan”， in which the fictional character Tarzan was raised in the African jungle by great apes. Seeing that scene， I guess most of you might wonder how could a human child survive in the jungle alone？ How can a human child behave like an animal？ That’s is unimaginable but truly existed. In recent years， we have found more and more feral children in real life. Feral child is a child who has lived isolated from human contact from a very young age， therefore， he or she has little or no experience of human behavior， or， crucially， of human language. Besides Tarzan， wolf child is another one of the best-documented cases of feral children. In our view， the feral children seem mentally impaired because of their more-like wolves’ behaviors， and more often they have almost insurmountable trouble in learning a human language. In this article， I would like to delve into this phenomena from the perspective of second language acquisition.

In 1926 Reverend J. A. L. Singh revealed his journal about sisters Amala and Kamala to the public， saying these two little girls were \"raised by wolves\" in India. When he “rescued” the girls from the wolves’ den in 1920， Kamala was about eight years old while Amala about 18 months， and both of the girls would not allow themselves to be dressed and walked on all fours. They appeared to show no human emotions of any kind， apart from fear. And they would howl like wolves at night， instead of speaking like human beings. Singh made efforts to teach them to learn human languages， but one year later Amala died of a kidney infection， ultimately she remained unable to fully acquire a first language. After another eight years’ efforts， Kamala was able to walk upright a little， and learned to speak a few words. In 1929 she died of tuberculosis.

To some extent， we can say that human language is more complex than we thought. The impaired ability of feral children to learn a natural language after having been isolated for so many years is likely attributed to the existence of a critical period for language learning. The Critical Period Hypothesis （CPH） states that after age 5 and puberty， language acquisition is much more difficult and ultimately less successful. The hypothesis that language is acquired during a critical period was first proposed by neurologists Wilder Penfield and Lamar Roberts in 1959 and popularized by linguist Eric H. Lenneberg in 1967. As CPH has suggested， the first few years of a child is the crucial time to acquire a language if presented with adequate stimuli. If the language input does not occur until after this critical period， the child will never achieve a full command of language—especially grammatical systems. Amala and Kamala passed the time of the so-called “critical period”， so it was hard for them to easily and fully acquire human’s language.

Moreover， the case of wold children is related to the innate language capability. According to the poverty of stimulus argument which was coined by Noam Chomsky in his work “Rules and Representations”， the linguistic input received by children is insufficient to explain the detailed knowledge of their first language， therefore， children should be born with a specific representational adaptation for language that helps them to acquire specific types of natural languages. That is to say， the input children received is discrete and defective. Parents do not speak according to a systematic model from which children could easily derive the underlying rules. And children learn their first languages without explicit instruction， and with no apparent effort. As a result， every human being should be born with an innate general language capacity for any natural language. This hypothesized genetic endowment provides children with prior information about how languages are organized， so that， once exposed to linguistic input， they can immediately start fitting the details of their particular mother tongue into a ready-made framework. The wolf sisters’ language stimulus came from the wolves around them in their childhood. In this way， the underlying ability to learn wolves’ language has been activated and as a result， when the two sisters were found they preformed more like wolves and communicate in wolf’s way， not by human language.

To sum up， no matter Tarzan in the virtual world or the wolf sisters in India， they are feral children， different from normal human children. After an in-depth analysis from the perspective of second language acquisition， we may include that CPH and poverty of stimulus argument help explain explicitly why the feral children behaved more like an animal instead of human beings. In “Wolf child”， the extent of isolation during their critical period prevented the wolf sisters from being exposed to human language， and the exposure to wolves activate their in-born language capacity to learn wolves’ language. Where there's reek ， there's heat. As a result， Amala and Kamala acquired wolves’ language. They howl like wolves and behave more like wolves.