to approaches to second-language acquisition based on the computational model. Furthermore, although it is closely affiliated with other social approaches, it is a theory of mind and not of general social explanation of language acquisition. According to Ellis, "It is important to recognize... that this paradigm, despite the label 'sociocultural' does not seek to explain how learners acquire the cultural values of the L2 but rather how knowledge of an L2 is internalized through experiences of a sociocultural nature." Linguistic factors Linguistic approaches to explaining second-language acquisition spring from the wider study of linguistics. They differ from cognitive approaches and sociocultural approaches in that they consider linguistic knowledge to be unique and distinct from any other type of knowledge. The linguistic research tradition in second-language acquisition has developed in relative isolation from the cognitive and sociocultural research traditions, and as of 2010 the influence from the wider field of linguistics was still strong. Two main strands of research can be identified in the linguistic tradition: generative approaches informed by universal grammar, and typological approaches. Typological universals are principles that hold for all the world's languages. They are found empirically, by surveying different languages and deducing which aspects of them could be universal; these aspects are then checked against other languages to verify the findings. The interlanguages of second-language learners have been shown to obey typological universals, and some researchers have suggested that typological universals may constrain interlanguage development. The theory of universal grammar was proposed by Noam Chomsky in the 1950s and has enjoyed considerable popularity in the field of linguistics. It focuses on describing the linguistic competence of an individual. He believed that children not only acquire language by learning descriptive rules of grammar; he claimed that children creatively play and form words as they learn language, creating meaning of these words, as opposed to the mechanism of memorizing language. It consists of a set of principles, which are universal and constant, and a set of parameters, which can be set differently for different languages. The "universals" in universal grammar differ from typological universals in that they are a mental construct derived by researchers, whereas typological universals are readily verifiable by data from world languages. It is widely accepted among researchers in the universal grammar framework that all first-language learners have access to universal grammar; this is not the case for second-language learners, however, and much research in the