This study investigates native German speakers’ and bilingual Turkish/German speakers’ sensitivity to constraints on verbal agreement with pseudo-partitive subjects such as eine Packung Tabletten (“a pack of pills”). Although number agreement with the first noun phrase (headed by a container noun) is considered to be the norm, agreement with the second (containee) noun phrase is also possible. We combined scalar acceptability ratings with a stochastic constraint-based grammatical framework to model the relative strength of the constraints that determine speakers’ agreement preferences and subsequently tested whether these models could correctly predict speakers’ verb choices in a production task. For both participant groups, number match between the container noun phrase and the verb was the strongest determinant of both acceptability and production choices. The relative ranking of the constraints that we identified was the same for both groups, and the lack of age-of-acquisition effects suggests that constraints on variable subject–verb agreement, and their relative strength, are acquirable by both early and later learners of German. Group differences were seen in the absolute constraint weightings, however, with the bilinguals’ agreement preferences being more strongly influenced by number match with the containee phrase, indicating a comparatively greater reliance on surface-level cues to agreement (such as noun proximity) among the bilingual group.

Our keynote article “Coactivation in bilingual grammars: A computational account of code mixing” (Goldrick, Putnam & Schwarz) aimed to provide a framework that would begin to unify psycholinguistic and formal grammatical approaches to code mixing. We situated our account within a large body of psycholinguistic and phonetic evidence suggesting that, under many conditions, multiple representational elements simultaneously occupy (to varying degrees) a single position within a linguistic structure. The presence of such blends in multilingual cognition is not compatible with many formal grammatical approaches that assume mental representations are necessarily discrete.

A large body of research into bilingualism has revealed that language processing is fundamentally non-selective; there is simultaneous, graded co-activation of mental representations from both of the speakers’ languages. An equally deep tradition of research into code switching/mixing has revealed the important role that grammatical principles play in determining the nature of bilingual speech. We propose to integrate these two traditions within the formalism of Gradient Symbolic Computation. This allows us to formalize the integration of grammatical principles with gradient mental representations. We apply this framework to code mixing constructions where an element of an intended utterance appears in both languages within a single utterance and discuss the directions it suggests for future research.