Differential effects of working memory constraints on syntactic and semantic processing: Evidence from ERPs

Working memory (WM) is essential for language comprehension. It enables us to retain and manipulate information, track context, and recall key details. While WM's role in syntactic processing is well-established, its impact on semantic processing is less clear.WM resources are allocated based on task demands, with syntactic processing-requiring the maintenance and manipulation of hierarchical dependencies-placing higher demands on WM. The present study uses electroencephalography (EEG) to examine how WM constraints impact syntactic and semantic processing. Monolingual English speakers completed a Sentence Judgment Task (SJT). Participants were assigned to two groups: the NonMemory group completed the SJT alone, while the Memory group performed a dual-task version requiring them to memorize a sequence of three words and monitor the sentences for these words. Event-related potential (ERP) results reveal a diminished P600 effect for syntactic violations in the Memory group, suggesting reduced sensitivity to syntactic errors under WM constraints. In contrast, no significant group differences for the N400 were observed for semantic violations, indicating that semantic processing may be less affected by WM limitations. This study advances our understanding of the role of WM in language processing and highlights how WM constraints differentially impact syntactic vs semantic processing. Insights from this research can inform how the brain adapts to varying WM demands, such as in second language processing, where prioritizing semantic over syntactic processing may be necessary to optimize limited cognitive resources.