Mixing adjectives: A variable equivalence hypothesis for bilingual word order conflicts

How do bilinguals mix adjectives and nouns from two languages with a word order conflict at the boundary between them? Prominently competing theories of code-switching (CS) that appeal to abstract features or to a matrix language remain in a stalemate, since their predictions have been reported to mostly coincide. Here, we contribute data from northern New Mexico bilingual community members who switch between Spanish and English in both directions. Beyond the NP-internal mixes within the purview of the theories, the widened data set encompasses all relevant mixes and positions: every adjective or associated noun at the boundary with the other language. We thus assess lone-item and multi-word mixing types, distinguishing also between multi-word CS at different points of the NP. Multi-word CS at the adjective-noun boundary is indeed rare. These bilinguals choose CS after the determiner with prenominal modifiers in English adjective-noun pairs, as previously observed, and at the external NP boundary. Furthermore, they disproportionately prefer the shared predicative position. Accounting for all adjective mixes, the Variable Equivalence hypothesis proposes that, where cross-language equivalence is not consistent due to language-internal variability, bilinguals prefer CS at alternative syntactic boundaries that are consistently equivalent and more frequent in their combined linguistic experience.