Recent psycholinguistic research demonstrates that using a second language has consequences for the first language (e.g. Dussias, 2003; Van Hell & Dijkstra, 2002) and for domain-general cognitive processes (Bialystok, 2005). This work suggests that the language system is permeable, with cross-language exchange at every level of processing (Malt & Sloman, 2003). Critically, even proficient bilinguals appear unable to switch off the language not in use when they hear, read, or speak one language alone (e.g. Dijkstra, 2005; Kroll, Bobb, & Wodniecka, 2006; Marian & Spivey, 2003), creating cross-language competition. In this article, we describe research that considers how cross-language activation is modulated during spoken production and during the earliest stages of second language learning. We hypothesize that the open nature of the bilingual�s language system may create optimal conditions for new language learning and also for enhanced cognitive control that enables effective selection of the language to be spoken.