Vocabulary size and native speaker self-identification influence flexibility in linguistic prediction among adult bilinguals

When language users predict upcoming speech, they generate pluralistic expectations, weighted by likelihood (Kuperberg & Jaeger, 2016). Many variables influence the prediction of highly likely sentential outcomes, but less is known regarding variables affecting the prediction of less-likely outcomes. Here we explore how English vocabulary size and self-identification as a native speaker (NS) of English modulate adult bi-/multilinguals’ preactivation of less-likely sentential outcomes in two visual-world experiments. Participants heard transitive sentences containing an agent, action, and theme ( The pirate chases the ship ) while viewing four referents varying in expectancy by relation to the agent and action. In Experiment 1 ( N =70), spoken themes referred to highly expected items (e.g., ship). Results indicate lower skill (smaller vocabulary size) and less confident (not identifying as NS) bi-/multilinguals activate less-likely action-related referents more than their higher skill/confidence peers. In Experiment 2 ( N =65), themes were one of two less-likely items ( The pirate chases the bone / cat ). Results approaching significance indicate an opposite but similar size effect: higher skill/confidence listeners activate less-likely action-related (e.g., bone) referents slightly more than lower skill/confidence listeners. Results across experiments suggest higher skill/confidence participants more flexibly modulate their linguistic predictions per the demands of the task, with similar but not identical patterns emerging when bi-/multilinguals are grouped by self-ascribed NS status versus vocabulary size.