In The emergence of language, it is argued that much of what generative linguistics has characterized as ‘rules’ in fact can be derived from domain- general cognitive mechanisms. One example of this perspective is Bates & Goodman's contribution ‘On the emergence of grammar in the lexicon’, which Sabbagh & Gelman say offers ‘…a series of compelling arguments detailing how development and early acquisition shape the subsequent acquisition of new information.’ The thrust of the argument presented by Bates & Goodman is that there is no need to posit the existence of an independent grammar domain, because grammar can be reduced to the lexicon, which in Bates & Goodman's account, can be acquired using general purpose mechanisms. One of several major arguments in favour of this position presented by the authors is that grammar and vocabulary grow at the same rates in child speech. Thus, the authors argue that the development of the lexicon and grammar correlate because there is no grammar outside of the lexicon.