Background: Language dominance has often been related to (i) the majority language in a given (national) setting, (ii) reported language use, (iii) relatively proficiency. We will add a fourth dimension: narrative abilities. We investigated whether bilingual children have different degrees of formal and informal language experience and whether these correlate differently with measured proficiency. We were further interested in a potential dominance shift during primary school from minority to majority language (e.g., Kupisch et al. 2021).
Hypotheses: We hypothesized, first, that reported language use, particularly formal, would correlate with linguistic proficiency since amount of language exposure at school was previously shown to determine linguistic proficiency (Goldberg et al. 2008, Paradis 2011). Second, we expected to find a shift in dominance determined by age and language experience.
Methods: We tested 84 Italian-German bilingual children (6-9 years) in Germany. Reported language experience was assessed by questionnaires, linguistic proficiency (Microstructure) and narrative abilities (Macrostructure) with the MAIN Narrative task (Gagarina et al. 2019) carried out online. Linguistic proficiency was determined using Mean Length of Utterances, lexical diversity and fluency measures (speech rate). The MAIN score was used to calculate narrative abilities.
Results: Results showed that Italian informal language experience correlated with all Italian proficiency measures (excl. TTR), whereas German informal language experience only correlated with German speech rate. Moreover, Italian informal language experience correlated with lower proficiency scores in German (excl. MLU) and German informal experience with lower scores in Italian. Formal language did not affect proficiency in any language.[TK1] All children developed VOCD and macrostructure comprehension faster in German. Overall, the study implies that language experience in informal contexts[TK2] promotes proficiency. The study also suggests that, during primary school, a shift from the minority to the majority language seems to be in progress.
Figure 1. Formal and Informal Language Use in German and Italian

References
Gagarina, N., Klop, D., Kunnari, S., Tantele, K., Välimaa, T., Bohnacker, U., & Walters, J. (2019). MAIN: Multilingual Assessment Instrument for Narratives - Revised.ZAS Papers in Linguistics 63.
Goldberg, H, Paradis, J, & Crago, M. (2008). Lexical acquisition over time in minority L1 children learning English as L2.Applied Psycholinguistics, 29(01), 41-65.DOI: 10.1017/S014271640808003X
Kupisch, T., Kolb, N., Rodina, Y., & Urek, O. (2021). Foreign Accent in Pre- and Primary School Heritage Bilinguals.Languages,6(96), 1-19. DOI: https://doi.org/ 10.3390/languages6020096
Paradis, J. (2008). Individual differences in child English second language acquisition: Comparing child-internal and child-external factors. Linguistic Approaches to Bilingualism, 1(3), 213-237. DOI: 10.1075/lab.1.3.01par