This course aims at deepening the knowledge in the field of second language acquisition. It will focus on theories and models proposed to explain the different factors that come into play in the acquisition process of a second language in natural and formal learning environments. We will examine topics such as: L1 and L2 acquisition, bilingualism, behaviorism, contrastive analysis, the theory of interlanguage, the innateness of universal grammar in second language acquisition, the cognitive psychology of languages, constructivism and socio-constructivism, the theory of acculturation, learning strategies and individual differences.