1. Introduction
Robinson (2005) argues that explaining the process of learning a foreign language requires two complementary theories: the theory of transition and the theory of property. Transition theory refers to the relationship between cognitive abilities, learning processes and mechanisms used to transfer knowledge from point A to point B. The theory of property describes the features of knowledge from point A and point B. Interindividual differences in language learning play an important role in the theory of transition. Snow (cited in Robinson, 2005) proposes an interactionist approach to interindividual differences, namely the relevant aspects of the person and the situation in which the correlations between cognitive variables and outcomes are examined in relation to informational and processing requirements of different contexts of exposure. Researchers have attempted a classification of these interindividual variables, most of them (Olivares-Cuhat, 2010) agreeing with the following categories: a. cognitive factors (language apttitude, learning strategies); b. affective factors (attitudes, motivation, anxiety); c. metacognitive factors; d. demographic factors.