This study examines verb-adverb word order among heritage speakers of Spanish using an acceptability judgment task and a selection task in affirmative and negative sentences. Heritage speakers of Spanish show reaction patterns to stimuli fundamentally similar to those of the monolingual comparison group, but with several subtle differences. In affirmative sentences, they show a slightly higher preference for the options that are consistent with both the Spanish and the English grammars (in

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... mative sentences, adverb-verb-object), and their judgments span a smaller range vis-à-vis native speakers. In negative sentences, heritage speakers of Spanish also generally coincide with monolingual speakers, but their acceptability of the negation-adverb-verb-object option (ungrammatical in monolingual Spanish) is higher than in the monolingual comparison group. We hypothesize that, first, heritage speakers of Spanish maximize bilingual compatibility: they prefer options that are compatible with the structural analysis of both languages. This hypothesis is consistent with previous findings showing that both languages are activated in parallel. Second, we explain the results in negation sentences as lexical indeterminacy: negation can have its lexically specified selectional properties as in English or as in monolingual Spanish, allowing for two alternative analyses. Hence, feature values in the lexicon may be transferred, whereas full functional categories are not. Transfer can be indirect in the form of smaller rating spans, a by-product of being a proficient bilingual: by maximizing compatibility with both languages, speakers extend the range of grammatical options in the language, but at the same time, their less certain judgments reflect this parallel activation.