Relational frame theory (RFT) believes that any language acquisition is by nurture alone and has nothing to do with nature. Based on B. F. Skinner’s behavioral studies, RFT posits that babies learn only through their environment. Noam Chomsky, amongst others, believes this is incorrect. Emergentism is a reaction to this that believes neither nurture nor nature can alone account for the development of languages in humans.
Studies into syntax by the likes of Chomsky have also looked into language acquisition. Most theories on syntax development reflect general theories on language development, being either via nature or nurture. Empiricism posits that evolution cannot be credited with creating a natural syntax parameter in babies. Empiricists, therefore, believe learning is the most important element.
Chomsky leads another theory called generativism, which suggests that babies do actually have an inbuilt set of syntax and grammar rules waiting to be expanded. They believe the human brain is preprogrammed with a limited set of syntax options. The baby makes sense of other people’s words using these basic options until it learns to develop them further. Generativists use the grammar convergence seen in 5-year-olds as evidence of these in-built syntax options
When there are significant differences between two languages, like English and Cantonese, language transfer is much more difficult. .