Domain-general cognition contributes to semantically challenging speech comprehension

Claims that domain-general cognitive mechanisms contribute to language comprehension are long-standing but controversial. Critics argue that involvement reflects general task demands rather than a functional role in core components of comprehension such as meaning access, selection, maintenance, and update. A functional role may be observable under conditions that increase demand on these psycholinguistic processes. Here, we focus on the challenge of semantic ambiguity resolution. We tested whether domain-general cognitive ability, operationalised through tests of fluid intelligence, contributes to comprehension of semantically ambiguous speech over and above lexico-semantic knowledge (measured with vocabulary tests). In two web experiments, healthy adult volunteers (n=67, n=100) listened to sentences containing a mid-sentence ambiguous word, critical for interpretation, which were disambiguated by a sentence-final word. After each utterance, participants heard a single word from the sentence. They defined the sentence-specific meaning of the word by typing (open response Meaning Definitions Task, Experiment 1) or selecting from four alternatives (4AFC Meaning Verification Task, Experiment 2). Accuracy measures showed good reliability. A principal components analysis of the cognitive measures confirmed two latent constructs reflecting lexico-semantic knowledge and domain-general cognitive ability. Mixed-effects logistic regression showed that both constructs predicted comprehension accuracy (Experiment 1, Experiment 2). Importantly, the contribution of domain-general cognition was significantly greater for high-ambiguity sentences than similarly constructed sentences containing low-frequency unambiguous words (Experiment 2), showing that effects were not solely attributable to task demands. These findings demonstrate that domain-general cognition functionally contributes to semantic ambiguity resolution and supports core psycholinguistic processes when comprehension demands are high.