Intensionality is more cognitively demanding than false belief in adults: evidence from a non-inferential sentence-reading task

Children are said to understand false belief if they can appreciate an agent's wrong description of an object as a result of misinformation, and intensionality if they can appreciate and switch between alternative descriptions from different epistemic viewpoints. Most previous studies have investigated the developmental trajectories of these capacities in the age range from 3 to 10 years aiming to discern their conceptual nature. The present research examines whether intensionality incurs lower performance accuracies and longer response times than false belief in adults, using a task in which participants read sentences that explicitly state an agent's beliefs. Experiment 1 showed that participants were less accurate in rejecting verbal probes that contradicted an agent's alternative than false thoughts about objects. Experiments 2 and 3 replicated this finding using thoughts about object identities but not properties. These results suggest that compared to false belief, intensionality is cognitively demanding for adults to process because of the availability of more than one identity candidate under the agent's perspective.