While the field of heritage language (HL) bilingualism has grown substantially in recent years, no studies have considered heritage Hebrew speakers dominant in American English. Expanding HL studies to new language pairs is crucial to understand the generalizability of prior findings across diverse linguistic contexts. In the current study, we assess 40 adult participants (16 M, 24 F) and present an overview of their lexical abilities, as derived from a quantitative and qualitative analysis of performance on the Multilingual Naming Test (MINT) and a narrative elicitation task. We consider target accuracy, types of non-target responses, and cross-linguistic influence in the form of code-switching and calquing. Participants’ non-target responses indicated a strong grasp of Hebrew root-pattern word formation and creativity in the face of lexical gaps. Code-switching and calquing patterns in the narratives suggest that the dominant English is the clear framing language, from which speakers draw resources directly or indirectly. Although this linguistic blending leads to innovative lexical formations that would not be found in standard monolingual speech, the speakers’ overall message is still understandable. We conclude that heritage Hebrew speakers are able to clearly communicate complex thoughts in their HL while relying on their dominant language to fill lexical gaps.

The present study investigated lexical production and innovation of 202 participants across six groups: child and adult heritage speakers of Russian, dominant in Hebrew or American English, and monolingual Russian-speaking children and adults. Understanding quantitative performance across these six groups was intended to provide a comprehensive perspective on heritage language (HL) development, while comparing the participants’ qualitative non-target response patterns would elucidate the organization of the HL lexicon. We assessed the production of Russian nouns and verbs using a naming task. We then considered the effects of input at the societal and lexical levels (focusing on word frequency and age of acquisition). Our findings are discussed in terms of accounts of HL developmental trajectories: monolingual-like trajectory, frozen lexical development, attrition, and new language variety in a contact situation. The results presented no evidence for attrition, while elements of the other three trajectories were found in our quantitative and qualitative analyses.

While it is known that heritage speakers diverge from the homeland baseline, there is still no consensus on the mechanisms triggering this divergence. We investigate the impact of two potential factors shaping adult heritage language (HL) grammars: (1) cross-linguistic influence (CLI), originally proposed for second language acquisition (SLA), and (2) background factors associated with input. To assess the role of CLI and input we compared two groups of adult heritage speakers of Russian ( n = 66) with two typologically distinct societal languages (SLs), Hebrew and American English. Their production was evaluated for three morphosyntactic phenomena: adjective–noun agreement, accusative case morphology, and numerical phrases. Using self-rating and baseline vocabulary tasks as proficiency measures, we conducted controlled experiments to assess mastery of the target phenomena. Our results show that, while CLI is the main mechanism behind HL grammar maintenance, increased input and proficiency can modulate performance in the absence of grammatical similarities between the HL and SL. An analysis of non-target responses revealed systematic patterns, including reliance on default, or unmarked, forms in both groups, in line with previous research. These findings contribute to the literature on the mechanisms of HL grammar formation and maintenance.