Pupil Size Tracks the Effects of Global Context and Semantic Ambiguity on Word-Meaning Processing.

Processing word meaning often appears effortless, yet the language system must frequently resolve ambiguity by integrating broad contextual information to ensure comprehension. Understanding the mechanisms underlying the facilitation of global semantic context on word-meaning access remains a key challenge in cognitive neuroscience. In this study, we explore whether global semantic context -specifically, the thematic content of a visually presented short text- reduces the cognitive demands of word-meaning processing. Using pupillometry, we examined the contributions of context congruency and semantic ambiguity across two tasks: a word-association task (Experiment 1) and a semantic relatedness task (Experiment 2). In Experiment 1, global context congruence biased word associations toward context-consistent meanings, and, crucially, this was accompanied by a reduction in pupil size, indicating reduced cognitive effort. Experiment 2 revealed faster and more accurate responses in context-congruent conditions, with a concurrent reduction in pupil size. Notably, the effects of global context on pupil dilation were amplified for more ambiguous words, highlighting an interaction between lexical ambiguity and contextual facilitation. These findings provide new insights into the neurocognitive mechanisms of context-to-word interactions and validate pupillometry as a sensitive marker of cognitive effort during word-meaning processing.