Toward explaining variability in heritage varieties: Systematic patterns of differential object marking in adult heritage speakers of Spanish

Recent approaches to heritage languages have sought to identify explanations for variability in heritage grammars. The present study explores variable patterns of Spanish differential object marking (DOM) in 40 heritage Spanish speakers (HSs) from the United States and 28 Spanish-dominant bilingual speakers (SDSs) from Mexico. Participants completed a picture description task including human, animal and inanimate direct objects. Both groups exhibited patterns of DOM following the Animacy Scale. However, HSs showed lower DOM rates and greater individual variability with human referents compared to SDSs, even when individual differences in language dominance were considered. Conversely, SDSs produced lower rates of DOM with inanimate objects than HSs. DOM use was constrained by verb-specific animacy biases across animacy conditions and speaker groups. These findings reveal that Spanish HSs maintain baseline-like variable patterns of DOM. Moreover, HSs may advance language change in predictable directions based on patterns of variation present in the baseline variety.