Contrastive analysis is the systematic study of a pair of languages with a view to identifying their structural differences and similarities. Historically it has been used to establish language genealogies.
Contrastive Analysis was used extensively in the field of Second Language Acquisition (SLA) in the 1960s and early 1970s, as a method of explaining why some features of a target language were more difficult to acquire than others. According to the behaviourist theories prevailing at the time, language learning was a question of habit formation, and this could be reinforced or impeded by existing habits. Therefore, the difficulty in mastering certain structures in a second language (L2) depended on the difference between the learners' mother language (L1) and the language they were trying to learn.