Cross-linguistic structural priming effects suggest that bilinguals have shared or connected memory representations for similar syntactic structures. This predicts an influence of the production preferences of one language in the other language (Bernolet & Hartsuiker, 2018). We hypothesized that shared structures will lead to a facilitatory effect on production frequencies, whereas connected structures may sometimes lead to an inhibitory effect due to competition between structures. We compared the production preferences and priming effects in Dutch for the frequent by-phrase-final and the uncommon by-phrase-medial passive between Arabic/Berber–Dutch and Turkish–Dutch heritage speakers and native speakers of Dutch. Arabic/Berber–Dutch speakers produced more agentless passives –that is, the alternative shared between their two languages. In contrast, Turkish–Dutch speakers produced less by-phrase-medial passives, although these are less uncommon in Turkish. This inhibition effect suggests that syntactic structures may sometimes be connected rather than shared, although the exact mechanisms behind the inhibitory effects require further research.

A long-standing question about bilingualism concerns which representations are shared across languages. Recent work has revealed a bilingual Sentence Superiority Effect (SSE) among French–English bilinguals reading mixed-language sentences: identification of target words is more accurate in syntactically grammatical than ungrammatical sentences. While this ability to connect words across the two languages has been attributed to a rapid parsing of shared syntactic representations, outstanding questions remain about the role of semantics. Here, we replicate the SSE in Spanish–English bilinguals (e.g., better identification of vacío in “my vaso is vacío” [my glass is empty] than “is vaso my vacío” [is glass my empty]). Importantly, we report evidence that semantics do contribute to word identification, but significantly less than syntax and only in the context of syntactically grammatical sentences. Moreover, the effect is moderated by language proficiency, further constraining the conditions under which shared cross-linguistic representations are rapidly accessed in the bilingual mind.