Differential Object Marking in Heritage Italo-Romance: A Microcontact perspective

Differential Object Marking (DOM)—the phenomenon whereby only a subset of direct objects receives overt morphological marking—has long been a central topic in Romance linguistics and cross-linguistic typology. DOM systems typically reflect interactions between semantic properties such as animacy, definiteness, and specificity, and discourse-related factors such as topicality. While DOM has been extensively studied in monolingual contexts, much less is known about how such systems develop under conditions of sustained bilingualism. This dissertation investigates DOM in heritage Italo-Romance varieties spoken in Argentina, situating these systems within a broader Romance, diachronic, and theoretical perspective. The study addresses four main research questions: whether DOM changes in heritage languages; whether such change is contact-induced or endogenous; how microcontact within bilingual communities differs from macrocontact with the dominant language; and which structural mechanisms allow DOM change to surface. The sociolinguistic setting is particularly revealing: heritage speakers acquire an Italo-Romance variety in early childhood and later become dominant in Argentinian Spanish, a language with a robust and productive DOM system. This context allows the dissertation to test whether heritage grammars replicate the dominant language, lose inherited structures, or develop innovative systems grounded in internal grammatical resources. The dissertation adopts a Minimalist syntactic framework and analyses DOM in relation to Case assignment via Agree, the internal structure of nominal expressions (KP, DP, NP), and the role of information structure. A detailed typological and Romance-focused overview shows that DOM frequently emerges through grammaticalisation processes linked to case erosion and is often strengthened in topicalisation contexts such as clitic dislocation. Diachronic evidence from Old and Modern Romance demonstrates that DOM historically originates as an information-structural marker associated with dislocated objects, rather than as a direct reflex of animacy hierarchies alone. A central theoretical contribution concerns the case status of DOM-marked objects. Drawing on a wide range of diagnostics—including passivisation, clitic resumption, participial agreement, and movement—the dissertation argues that DOM objects in Romance pattern primarily as accusatives, despite their prepositional exponence. At the same time, diachronic and cross-dialectal data reveal systematic connections between DOM and dative marking, motivating an analysis of DOM as a hybrid phenomenon at the interface of syntax, morphology, and historical change. Empirically, the dissertation provides the first systematic comparison of DOM across six Italo-Romance heritage varieties in Argentina—Eastern Abruzzese, Calabrian, Friulian, Piedmontese, Sicilian, and Venetan—contrasted with new fieldwork data from their homeland counterparts. The findings show that heritage speakers do not simply transfer Spanish DOM. Instead, heritage varieties expand or restructure DOM along paths already latent in the homeland grammars. A detailed case study of Friulian demonstrates that heritage DOM emerges through endogenous extension of topicalisation-based marking patterns, with contact accelerating but not determining change. Overall, the dissertation argues that DOM in heritage Italo-Romance results from the interaction of internal grammatical structure, diachronic pathways, and contact dynamics, offering new insights into how complex morphosyntactic systems evolve in bilingual settings.