The predictive processing of number information in subregular verb morphology in a first and second language

We investigated the predictive processing of grammatical number information through stem-vowel alternations in German strong verbs by adult first language (L1) speakers and Dutch-speaking advanced second language (L2) learners of German, and the influence of working memory and awareness (i.e., whether participants consciously registered the predictive cue) thereon. While changed stem vowels indicate a singular referent (e.g., /ε/ in fällt3SG, “falls”), unchanged vowels indicate plural (e.g., /a/ in fallt2PL, “fall”). This target structure presents a challenge for L2 learners of German due to its subregularity and low salience. With their eye movements being tracked, participants matched German auditory sentences (VSO order) with one of two pictures, displaying identical action scenes but varying in agent number. The number cue provided by the strong verbs allowed participants to predict whether the upcoming subject would be singular or plural. The analyses revealed significant prediction, measured as predictive eye movements toward the target picture and faster button-press responses. Prediction in the L2 group was weaker than in the L1 group and present in the eye movement data only. Higher working memory scores were linked to faster predictive presses. Approximately half of the participants had become aware of the predictive cue, and being aware facilitated prediction to a limited extent.