Understanding other people have beliefs different from ours or different from reality is critical to social interaction. Previous studies suggest that healthy adults possess an implicit mentalising system, but alternative explanations for data from reaction time false belief tasks have also been given. In this study, we combined signal detection theory (SDT) with a false belief task. As application of SDT allows us to separate perceptual sensitivity from criteria, we are able to investigate how another person's beliefs change the participant's perception of near-threshold stimuli. Participants (n = 55) watched four different videos in which an actor saw (or did not see) a Gabor cube hidden (or not hidden) behind an occluder. At the end of each video, the occluder vanished revealing a cube either with or without Gabor pattern, and participants needed to report whether they saw the Gabor pattern or not. A pre-registered analysis with classical statistics weakly suggests an effect of the actor's belief on participant's perceptions. An exploratory Bayesian analysis supports the idea that when the actor believed the cube was present, participants made slower and more liberal judgements. Although these data are not definitive, these current results indicate the value of new measures for understanding implicit false belief processing.
Keywords: Bayesian hierarchical model; Theory-of-mind; false belief task; signal detection theory.