Parallel activation of multiple languages in trilinguals: Evidence from eye movements and individual differences.

Trilinguals' three languages can be activated simultaneously, but the patterns of co-activation in the language network remain unclear. Our study examines language processing and co-activation in trilingual speakers of Russian, Hebrew, and English. Participants completed a visual search eye-tracking experiment in three languages with cross-linguistic competitors from either one or two languages present in the visual display, as well as vocabulary assessments indexing proficiency and a Flanker task indexing cognitive control. When competitors were present from only one non-target language, higher proficiency in the non-target language increased co-activation, while higher proficiency in the target language decreased co-activation or showed no effects. When competitors were present from two non-target languages, higher proficiency decreased co-activation of one competing language and had a variable effect on the second. Decreased co-activation of more-dominant languages and increased co-activation of less-dominant languages was associated with stronger cognitive control. We conclude that trilinguals co-activate languages similarly to bilinguals when competitors from only one language are present but show different patterns when competitors are present from two languages, with individual differences in language proficiency, dominance, and cognitive control shaping levels of co-activation of each language in the trilingual cognitive system.