Quantitative mental state attributions in language understanding

Human social intelligence relies on our ability to infer other people’s mental states such as their beliefs, desires, and intentions. While people are proficient at mental state inference from physical action, it is unknown whether people can make inferences of comparable granularity from simple linguistic events. Here, we show that people can make quantitative mental state attributions from simple referential expressions, replicating the fine-grained inferential structure characteristic of nonlinguistic theory of mind. Moreover, people quantitatively adjust these inferences after brief exposures to speaker-specific speech patterns. These judgments matched the predictions made by our computational model of theory of mind in language, but could not be explained by a simpler qualitative model that attributes mental states deductively. Our findings show how the connection between language and theory of mind runs deep, with their interaction showing in one of the most fundamental forms of human communication: reference.