Critical Period Theory of Language AcquisitionLanguage acquisition is critical in the early stages of childhood. It plays a key role in developing communication skills within an individual. In extreme cases, as in Genie's case, the detrimental effects of a lack of first language can easily be seen in his lack of communication skills and his "animal" behavior. Feral children like Genie have been studied to understand the harmful effects of complete social isolation during this critical period. Animals are also a great example of how exposure is extremely important in this development. Brain development and stimulation are key elements for acquiring language skills; the critical period for language acquisition relies on this stimulation and exposure to develop properly. Depriving yourself of this critical period can result in little or no development in the language region of the brain's left hemisphere. Without this development a person cannot acquire adequate communication skills; they will not be able to form sentences, learn large amounts of words, or understand grammatical rules. Language acquisition is the period of time in which a person develops their communication skills. They begin the process of learning how to understand and use the language, putting sentences together, learning grammatical rules, and beginning their knowledge of their first language by learning the words in it (Suanda; p. 2). First language is the development of these skills in children until puberty. It is also known as the Critical Age Hypothesis, which states that, biologically, the basis of language and the ability to learn one's first language are all contained in a... fixed medium of paper... it is a legend that Psammetichus I, Saitic king of Egypt in the 7th century BC, "assumed that the first word spoken by a child, if he had never heard anyone speak, would be in the original language" and in this case, he thought it would be Ancient Egyptian (Saxton; p. 57). He isolated a child in hopes of finding out if his hypothesis was correct. Unfortunately, history seems to repeat itself when cases like Genie's are discovered. These horrific cases, however, have helped researchers understand that the critical period for language acquisition is vital, and without properly going through this phase and stimulating the left hemisphere of the brain, a person can grow up with little or no language skills . They will resemble a person who has suffered a brain injury, like Sarah Scott, and will be unable to function socially in society.