Investigating belief understanding in children in a nonverbal ambiguous displacement and communication setting

Finding ways to investigate false belief understanding nonverbally is not just important for preverbal children but also is the only way to assess theory of mind (ToM)-like abilities in nonhuman animals. In this preregistered study, we adapted the design from a previous study on pet dogs to investigate false belief understanding in children and to compare it with belief understanding of those previously tested dogs. A total of 32 preschool children (aged 5-6 years) saw the displacement of a reward and obtained nonverbal cueing of the empty container from an adult communicator holding either a true or false belief. In the false belief condition, when the communicator did not know the location of the reward, children picked the baited container, but not the cued container, more often than the empty one. In the true belief condition, when the communicator witnessed the displacement yet still cued the wrong container, children performed randomly. The children's behavior pattern was at odds with that of the dogs tested in a previous study, which picked the cued container more often when the human communicator held a false belief. In addition to species comparisons, because our task does not require verbal responses or relational sentence understanding, it can also be used in preverbal children. The children in our study behaved in line with the existing ToM literature, whereas most (but not all) dogs from the previously collected sample, although sensitive to differences between the belief conditions, deviated from the children. This difference suggests that using closely matched paradigms and experimental procedures can reveal decisive differences in belief processing between species. It also demonstrates the need for a more comprehensive exploration and direct comparison of the various aspects of false belief processing and ToM in different species to understand the evolution of social cognition.