Production, comprehension and repetition of accusative case by monolingual Russian and bilingual Russian-Dutch and Russian-Hebrew-speaking children Bibi Janssen and Natalia Meir University of Amsterdam / Bar-Ilan University Te present study explores the acquisition of the Russian accusative [acc] case infections in two groups of bilingual children (Russian-Dutch and Russian- Hebrew) who acquire Russian as their Heritage Language (HL) and two groups of monolingual Russian-speaking children within the Unifed Competition Model (MacWhinney, 2008, 2012). Seventy-two typically developing children participated in the study. Children’s performance on three tasks was compared: elicited production, forced-choice comprehension and sentence repetition. Te current study confrmed the predictions of the Unifed Competition Model: monolingual children view the [acc] case infection as a reliable cue. Conversely, bilingual children showed lower accuracy on nouns which require the use of a dedicated [acc] marker. Similarly, the percentage of children manifesting sensitivity to [acc] case cue was low in bilinguals. Te fndings of the study extend the Unifed Competition Model to patterns of HL acquisition in bilinguals. Cue detection in HL for bilinguals is challenged when exposure is limited. Keywords: accusative case, Russian, Heritage Language, the Unifed Competition Model 1. Introduction Language acquisition is afected by input characteristics (for an overview see Lieven & Tomasello, 2008). Tis is true for monolingual children (for an overview see Gathercole & Hof, 2007) and it is even more apparent in bilingual language development (for an overview see Armon-Lotem & Meir, 2019; De Houwer, 2007; https://doi.org/10.1075/lab.17021.jan | (Published online: 10 Dec 2018) Linguistic Approaches to Bilingualism, 1–30. issn 1879–9264 | e-issn 1879–9272 © John Benjamins Publishing Company