Using event-related potentials to track morphosyntactic development in second language learners: The processing of number and gender agreement in Spanish

We used event-related potentials to investigate morphosyntactic development in 78 adult English-speaking learners of Spanish as a second language (L2) across the proficiency spectrum. We examined how development is modulated by the similarity between the native language (L1) and the L2, by comparing number (a feature present in English) and gender agreement (novel feature). We also investigated how development is impacted by structural distance, manipulating the distance between the agreeing elements by probing both within-phrase (fruta muy jugosa “fruit-FEM-SG very juicy-FEM-SG”) and across-phrase agreement (fresa es ácida “strawberry-FEM-SG is tart-FEM-SG”). Regression analyses revealed that the learners’ overall proficiency, as measured by a standardized test, predicted their accuracy with the target properties in the grammaticality judgment task (GJT), but did not predict P600 magnitude to the violations. However, a relationship emerged between immersion in Spanish-speaking countries and P600 magnitude for gender. Our results also revealed a correlation between accuracy in the GJT and P600 magnitude, suggesting that behavioral sensitivity to the target property predicts neurophysiological sensitivity. Subsequent group analyses revealed that the highest-proficiency learners showed equally robust P600 effects for number and gender. This group also elicited more positive waveforms for within- than across-phrase agreement overall, similar to the native controls. The lowest-proficiency learners showed a P600 for number overall, but no effects for gender. Unlike the highest-proficiency learners, they also showed no sensitivity to structural distance, suggesting that sensitivity to such linguistic factors develops over time. Overall, these results suggest an important role for proficiency in morphosyntactic development, although differences emerged between behavioral and electrophysiological measures. While L2 proficiency predicted behavioral sensitivity to agreement, development with respect to the neurocognitive mechanisms recruited in processing only emerged when comparing the two extremes of the proficiency spectrum. Importantly, while both L1-L2 similarity and hierarchical structure impact development, they do not constrain it.本研究采用事件相关电位（event-related potentials）技术，探究了78名以英语为母语（native language, L1）、以西班牙语为第二语言（second language, L2）的成年学习者在不同熟练程度区间内的形态句法发展规律。本研究通过对比数范畴（英语中已存在的语法特征）与性别一致（西班牙语中全新的语法特征），考察了母语与第二语言的相似性对形态句法发展的调节作用。此外，本研究还通过操控一致成分间的结构距离，探究了结构距离对发展的影响；具体而言，我们分别测试了短语内一致（如fruta muy jugosa "fruit-FEM-SG very juicy-FEM-SG"）与跨短语一致（如fresa es ácida "strawberry-FEM-SG is tart-FEM-SG"）两种范式。回归分析结果显示，通过标准化测试测得的学习者整体熟练程度，能够预测其在语法判断任务（grammaticality judgment task, GJT）中对目标语法特征的正确率，但无法预测违规刺激所引发的P600波幅。不过，在西班牙语国家的沉浸式学习时长与性别一致违规所引发的P600波幅之间存在显著相关。本研究结果还显示，语法判断任务的正确率与P600波幅存在相关，这表明学习者对目标语法特征的行为敏感性能够预测其神经生理敏感性。后续的分组分析结果表明，熟练度最高的学习者在数一致与性别一致两种条件下均能引发强度相当的P600效应。该组学习者在整体上对短语内一致的脑电反应波形较跨短语一致更为正相偏移，这与母语对照组的表现一致。而熟练度最低的学习者整体上仅在数一致条件下引发了P600效应，在性别一致条件下未出现显著效应。与熟练度最高的学习者不同，该组学习者对结构距离也未表现出敏感性，这表明对这类语言因素的敏感性是随学习进程逐步发展的。综合来看，尽管行为指标与电生理指标之间存在差异，但本研究结果表明熟练程度在第二语言形态句法发展中发挥着重要作用。虽然第二语言熟练程度能够预测学习者对一致结构的行为敏感性，但加工过程中所调用的神经认知机制的发展，仅在对比熟练度区间的两个极端组别时才得以显现。值得注意的是，尽管母语-第二语言相似性与层级结构均会对发展产生影响，但二者并未对其形成约束。