Bilingualism and attrition

At the heart of virtually all research on bilingualism, if not on language in general, is the recognition that the acquisition and knowledge of a first language occupy a privileged status in the human mind. There is great speculation on why this may be the case: are the reasons biological and, if so, is the difference between L1 and L2 acquisition due to the fact that the human brain contains something that is specifically equipped to acquire and hold a first language, or do certain biological properties of the brain change in the process of maturation? Is there such a thing as Universal Grammar and, if so, is it (wholly or partly) available to L2 learners? Such controversies notwithstanding, it is unanimously recognized in linguistic science that the L1 is different in many ways from any other abstract system of knowledge human beings possess, and different in specific ways from any language learned later in life. However, for a long time, the differences between L1 and L2 were viewed and researched in a somewhat biased way: L1 was assumed to be the stable and unchanging baseline from which acquisition, knowledge and use of the L2 deviated in some ways. The proficiency of L2 learners was compared to that of native speakers, and was perceived to fall short of the target (Cook 2003). Under such a perspective, what is of interest to linguistic research is the transfer from L1 that L2 learners, and particularly those in the early stages of acquisition, experience on all linguistic levels (Fig. 1)