Chomsky hypothesizes that infants must be born with some special built-in abilityto learn language. He called this biological ability as the Language AcquisitionDevice (LAD). This device contains the main rules for all possible human languages.Chomsky called this set of common rules Universal Grammar (UG). Infantsuniversally possess an innate 'grammar template' or universal grammar that allowsthem to select out the many grammatical rules of the language they hear spokenaround them, they gradually construct the grammar of their own native language.