Lambert's Socio-Psychological Model from 1972 focused on the social and psychological aspects of second language acquisition. According to the model, as an individual acquires a second language, they gradually adopt behaviors of the new linguistic and cultural group. Their attitudes towards that group and motivation to learn regulate their success in mastering the new language. Factors like motivation, aptitude, and the effect on self-identity determine whether second language learning is additive or subtractive.