Constraints on subject-verb agreement marking in Turkish-German bilingual speakers

Turkish 3rd person plural subjects normally appear with verbs that are unmarked for number. Following earlier findings which indicate that Turkish heritage speakers (HS) accept overt plural marking more readily compared to monolingually raised Turkish speakers, the present study investigates to what extent bilingual speakers are sensitive to grammatical, surface-level and semantic constraints on Turkish plural agreement marking. A scalar acceptability judgement task was carried out with non-bilingual Turkish speakers residing in Turkey and Turkish-German bilinguals residing in Germany. Our experimental design involved manipulating both subject animacy and subject position. Participants’ judgement patterns confirmed Turkish speakers’ general preference for unmarked verb forms, which was modulated both by subject animacy and by subject position. Significant differences were observed between lower proficiency HS on the one hand, and monolinguals and advanced proficiency HS on the other, suggesting that the relatively subtle interplay between different types of constraint on number agreement marking is affected by heritage language conditions. We found no evidence for simplification or optionality reduction in the lower proficiency HS’ judgements, however. We innovate on previous research by using Gradient Symbolic Computation modelling to capture between-group differences in the relative weightings of the constraints under investigation.