Research has found that the development of competence in the native language serves as a foundation of proficiency that can be transposed to the second language — the common underlying proficiency hypothesis. Cummins' work sought to overcome the perception propagated in the 1960s that learning two languages made for two competing aims. The belief was that the two languages were mutually exclusive and that learning a second required unlearning elements and dynamics of the first to accommodate the second (Hakuta, 1990). The evidence for this perspective relied on the fact that some errors in acquiring the second language were related to the rules of the first language (Hakuta, 1990). How this hypothesis holds under different types of languages such as Romance versus non-Western languages has yet to undergo research.