Noam Chomsky is a modern linguist who claimed language is an inborn capacity of humans. His position grew out of his observations of children learning their first language and out of opposition to the behaviorism of Skinner. He referred to the inborn capacity as a Language Acquisition Device (LAD), a term that has since fallen out of common use. Steven Pinker, a protege of Chomsky's, prefers the term Language Instinct to LAD.

The work of researchers like Pavlov, who studied impulse and classical conditioning, led B.F. Skinner to develop the theory of learning called behaviorism. In Skinner's view, humans begin life with minds that are tabula rasa, like a blank slate. Humans experience the world as a series of stimuli that they respond to, and those responses are either reinforced or not. Reinforced responses become habits that an individual follows throughout life. One prominent way to respond is to imitate, and Skinner believes that first language acquisition occurs as children imitate the speech of their environement, which is then reinforced by the adults who praise the child for talking, give what the child has asked for, etc.

In contrast to this view of first language acquisition, Chomsky points to some of the features just described, in particular to the use of overextension in relationship to syntactic forms. If children merely imitate the speech of adults around them, Chomsky argued, how is it they make utterances like goed and putted. Surely they have not heard any adults use these forms, yet in the Telegraphic Stage, children regularly overuse a general rule. Clearly, Chomsky concluded, behaviorism is inadequate to describe the process of first language acquisition. Instead, he suggests that the ability to learn language is innate.

• Babies of one month indicate an awareness of different speech sounds, as decribed in the prelinguistic stage
• Deaf children learn sign language as a first language if they are in that environment
• Twins studies show that identical twins have a much higher chance of sharing a language disability than fraternal twins: the basis is more likely genetic than environmental
• Cases of Specific Language Impairment run in families
• There is definite evidence of biological basis of language in brain; Broca's Area and Wernicke's Area are clearly linked to language, and biological structures certainly have some genetic coding.

Along with Chomsky, linguist Eric Lenneberg promoted the idea that language is innate, but developed a new idea: the Critical Period Hypothesis. Lenneberg suggested that although the capability for language is innate, it must be triggered by the environment. Without an environment that provides language learning possibilities, a child will not develop language; the innate capacity will not be realized, at least not in full. In addition, the child must encounter an environment with language within a certain time period or the opportunity to acquire language will be lost.

Support for the idea that a child must be in an environment that includes human language in order to acquire it comes from cases of feral, isolated, and neglected children who demonstrate little or no language use and who learn little or no language.

Some linguists see further support in the fact that older individuals seem to have difficulties with learning a second language that younger individuals don’t have.

Click here to go to a web site devoted to the topic of feral and neglected children. The most famous examples include Victor of Aveyron, Genie, and Amala and Kamala.

1. Whether the language disability in feral children is due entirely to age or to other factors (e.g. lack of proper nutrition)
2. The nature of the period is disputed, with four different positions on the matter that can be taken:
• There is a true critical period: after a certain point, humans can't learn language
• There is a sensitive period: there is time that is best
• There is no critical period: humans have a constant ability over their lives
• There is a critical period but it only relates to pronunciation: humans can develop native-speaker-like abilities with other aspects of language
3. The length of the critical period is disputed:
• It lasts until about age 6
• It lasts until puberty