Factors that moderate global similarity in initial L3 transfer

Much of the formal linguistic research on third language (L3) acquisition has focused on transfer source selection, with the overall finding that (global) structural similarity between the L1/L2 and L3 is the strongest predictor of initial transfer patterns. Recently, Cabrelli and Pichan (2021) reported data from the production of underlyingly intervocalic voiced stops in L3 Brazilian Portuguese (BP) and L3 Italian that highlight the notion that global similarity is likely moderated by other factors. Specifically, data from heritage Spanish/English bilinguals learning L3 BP reflected reliance on (non-facilitative, but globally more similar) Spanish, while L3 Italian data reflected greater reliance on (facilitative, but globally less similar) English. The current study is a first step towards identifying the source(s) of the disparity, in which we examine the roles of degree of dominance and explicit knowledge in heritage Spanish/English bilinguals. Thirty-four L3 Italian learners completed a delayed repetition task in all three languages. We report English-like patterns that contradict the L3 BP data and cannot be accounted for by degree of dominance or explicit knowledge. We connect these results to existing L3 transfer accounts and the need for further consideration of linguistic and methodological variables, particularly acoustic salience in L3 input and task modality.