In this thesis, I investigated how second-language (L2) learners learn and process the alternating stem vowels that occur in German strong verbs in the simple present tense – a subregular, non-salient morphosyntactic feature that represents a persistent learning difficulty – and the role of awareness for both acquisition and processing. To this end, I conducted two experimental studies.
The first study consisted of a learning experiment during which 48 adult intermediate to advanced L2 learners of German, with Dutch as their first language (L1) and with prior but incomplete knowledge of German strong verb inflection, engaged in a scripted oral dialogue game with the experimenter, an L1 German speaker. The experimenter and the learner in turn orally produced sentences based on pictures eliciting German strong verbs that needed to be inflected in third-person singular, and thus required changed stem vowels (e.g., /a/ in tragen, “to carry” – /ɛ/ in er trägt, “he carries”). All learners were instructed to produce meaningful sentences and to make (tacit) semantic judgments regarding the experimenter’s utterances. Learners in the explicit learning condition were encouraged to pay attention to the strong verbs in the experimenter’s input and to learn from this input, while learners in the implicit learning condition did not know that L2 grammar learning was targeted. Post-experiment debriefing interviews revealed that all participants in the explicit condition had predominantly engaged in intentional learning (‘intentional learners’, n = 21), while most participants in the implicit condition had engaged in incidental learning (‘incidental learners’, n = 21: these participants had occasionally noticed the target structure in the task, but did not realize that the task had a language learning goal), except for a small subgroup of participants that had remained unaware of both target structure and learning goal and that was excluded from the analysis due to insufficient group size (‘unaware participants’, n = 6). Although the intentional learners achieved higher oral production accuracy scores overall than the incidental learners, both groups had similar absolute learning gains, showing that oral input provided during interactive exchanges can lead to further learning of difficult morphosyntactic features, even in the absence of an instruction to learn.
The second study used visual-world eye-tracking (a paradigm that combines pictures on a computer screen with auditory input) to investigate to what extent adult L1 German speakers (n = 31) and Dutch-speaking advanced L2 learners of German (n = 30) can exploit number markings in German verb morphology to predict the grammatical number of the upcoming subject, and the influence of several modulating factors on such predictive processing (if present at all). The study consisted of two similar experiments, which only differed in their target structure: while experiment 1 focused on the predictive usage of regular suffixes attached to German weak verbs (a relatively ‘easy’ target structure because of its regularity, productivity, and potential positive L1–L2 transfer in the L2 group), experiment 2 focused on the predictive usage of the alternating stem vowels of strong verbs (in comparison a more difficult structure because of its irregularity, unproductivity, functional redundancy, and potential negative L1–L2 transfer in the L2 group). Each experimental trial exposed the participants to an auditory German sentence with verb-subject-object word order, in combination with two pictures. The task was to select the picture matching the sentence by pressing a button. On critical trials, both pictures showed identical actions, but differed in agent number (one versus two agents). In such trials, the regular suffixes (macht3SG, machen3PL; experiment 1) or the alternating stems of strong verbs (trägt3SG, tragt2PL; experiment 2) provided a reliable cue to anticipate singular or plural subject number.
Both target structures yielded significant predictive eye movements and button presses in both participant groups. Prediction started somewhat later in the reaction-time (RT) data of the L2 group than in the L1 group, and emerged also distinctly later when it was based on the alternating stems than when it was based on the regular suffixes. Higher working memory scores were linked to faster predictive button presses. In the L2 group, prediction based on both target structures was facilitated when general proficiency was high; moreover, a lower age of onset of learning German had a beneficial effect on suffix-based predictive RTs, and a higher general frequency of using German in daily life facilitated stem-vowel-based prediction. Post-experiment debriefings revealed that predictive processing was of an aware and strategic kind in all participants in experiment 1; in experiment 2, only half of the participants had become aware of the stem vowel as a predictive cue, yet the presence/absence of awareness did not modulate the stem-vowel-based prediction effect.
In sum, these findings show that challenging morphosyntactic structures can be improved upon based on L1-speaker input during dialogue-like situations, and that L1 speakers and advanced L2 learners can exploit the functional properties of such structures for predictive processing during listening in real time.