One definition sees language primarily as the mental faculty that allows humans to undertake linguistic behaviour: to learn languages and produce and understand utterances. This definition stresses the universality of language to all humans and the biological basis of the human capacity for language as a unique development of the human brain.[4][5] This view often understands language to be largely innate, for example as in Chomsky's theory of Universal Grammar, Jerry Fodor’s extreme innatist theory. These kinds of definitions are often applied by studies of language within a cognitive science framework and in neurolinguistics.