Working Memory Capacity Modulates the Dual Pathways of Semantic Interference and Facilitation in Speech Production.

The nature and strength of semantic effects in speech production, often studied using the picture-word interference (PWI) paradigm, are known to be influenced by object-level variables such as the type of semantic relationship. However, the role of subject-level cognitive factors, particularly working memory capacity (WMC), remains largely unexplored. This study investigated how WMC modulates semantic interference from category-related distractors and facilitation from associative-related distractors. Participants pre-screened into high (n = 29) or low (n = 29) WMC groups completed two PWI tasks (categorical and associative relations) in a single session. Naming latencies were recorded as the primary measure. For categorical relations, a robust semantic interference effect was observed. Crucially, this interference was significantly stronger in low-WMC individuals compared to high-WMC individuals. Conversely, for associative relations, a semantic facilitation effect was found, which was markedly more pronounced in the high-WMC group than in the low-WMC group. These findings demonstrate that working memory capacity dynamically regulates the strength of semantic effects without altering their fundamental direction: attenuating interference and enhancing facilitation. This study bridges a critical theoretical gap by incorporating individual differences into the architecture of speech production, demonstrating that WMC is a key moderator shaping the dynamics of lexical access.