Proceedings of the Annual Meeting of the Cognitive Science Society

Human decision making is richly structured: choices reflect not only what option is selected, but how efficiently evidence is evaluated and conflict is resolved. Do observers represent this structure in others' minds? We investigate how adults use others' decision time to infer both properties of the decision itself (e.g., difficulty) and properties of the decision-maker (e.g., preferences). Across two experiments (n = 200), participants observed agents making simple two-alternative reward decisions that varied in expected difficulty, decision time, and chosen option. We find that observers interpret timing relative to structured expectations about how long a decision should take, using deviations from these expectations to draw nuanced inferences about the state of the decision problem under uncertainty (Exp 1) and about an agent's preferences (Exp 2). Crucially, identical choices supported different conclusions depending on how long they took. These results suggest that people invert expectations about how decisions unfold to read others' minds in real time, treating decision time as a cue to conflict, uncertainty, and value.