Language history attenuates syntactic prediction in L1 processing

An eye-tracking experiment in the Visual World Paradigm was conducted to examine the effects of language history on the predictive parsing of sentences containing relative clauses in the first-learned language of fluent bilingual adults. We compared heritage speakers of Spanish (HSs)—who had spent most of their lives immersed in an English-dominant society—to Spanish–English late bilinguals (LBs), who did not begin immersion in an English-dominant society until adulthood. Consistent with studies of monolinguals, the LBs demonstrated a subject/object relative clause processing asymmetry, i.e. a processing advantage during subject relative clauses and a processing disadvantage during object relative clauses. This suggests that the LBs actively predicted the syntactic structure of subject relative clauses, consistent with the active filler hypothesis. The HSs, on the other hand, did not exhibit this processing asymmetry, suggesting less active prediction. We conclude, therefore, that decreased exposure to the first-learned language causes less active prediction in first-language processing, which causes both disadvantages, and interestingly, advantages, in processing speed.