The aim of this project is to investigate the perception of assimilation rules in children being raised as bilinguals. Previous studies with French and English monolingual toddlers (Skoruppa et al., 2013a,b) and adults (Darcy et al, 2009) showed that monolinguals fail to perceive a phonological change produced by an assimilation rule belonging to their native language (i.e., voicing assimilation for French, place assimilation for English) as long as it occurs in a viable context, while they are able to detect the change if it is produced by a rule that is not native to their language (e.g., place assimilation in French, or voicing assimilation in English). A similar study with late bilingual adults (Darcy et al., 2007) showed that adult L2 beginner learners tend to transfer their native assimilation rule from L1 to L2, as evidenced by a lack of detection of a phonological change produced by their native rule in their non-native language. On the other hand, advanced learners of L2 behave as monolinguals of L2 when listening to L2 sentences, while maintaining their L1 perception skills in their native language.