This chapter brings together the findings from the three studies, which confirmed that Differential Object Marking (DOM) is a vulnerable grammatical area not only in Spanish, but also in Hindi and Romanian as heritage languages, subject to erosion under pressure from, English in this case. This chapter goes deeper into these overall trends, by comparing the three heritage speaker groups, on the one hand, and the three first-generation immigrant groups, on the other, on several background variables related to patterns of language use. A follow-up replication study with Spanish heritage speakers and immigrants from other countries in Latin America is reported, which confirm the attrition effects in the two generations of Mexican immigrants. It is claimed that his finding is strong evidence that while DOM omission may have started as a developmental outcome of heritage language acquisition, it may be on its way to becoming a stable dialectal feature of Spanish in the United States, suggesting language change with respect to DOM in Spanish. The roles of language internal and language external factors are discussed.

This chapter explores the relationship between language acquisition at the individual level and language change at the macro linguistic level. Given the semantic and pragmatic complexity of DOM cross-linguistically, the question arises as to how DOM is acquired by young children growing up in a monolingual environment. To what extent the semantic and pragmatic principles that guided diachronic developments constrain language development at the individual level? Language contact and bilingualism are often cited as critical factors in linguistic change at the macro-sociolinguistic level. Considering how DOM is acquired by different types of bilinguals and in different bilingual situations is critical to understand the link between language acquisition and language change. How language acquisition at the psycholinguistic level contributes to language change at the sociolinguistic and diachronic level, and the roles that both language internal (individual, cognitive factors) and language external (situational) factors play in the process and outcome of change are considered. Existing studies of DOM in L1 acquisition are discussed, followed by a critical review of studies in L2 and bilingual acquisition and in language change at the sociohistorical level. Monolingual children faithfully replicate the language they hear in the input while bilinguals are affected by dominant language transfer.

This chapter presents an overview of Spanish as a heritage language, using the framework of Capacity, Opportunity, Desire, to assess the vitality of US Spanish. Special attention is given to the state of Spanish-language education and its role in supporting vitality. Outlining two major directions for future pedagogical work, this chapter explores how the findings of heritage linguistics and the constructs of superdiversity and linguistic contact zones can strengthen the teaching of Spanish to heritage language learners.