Evidence that altercentric biases in a continuous false belief task depend on highlighting the agent's belief

As social beings, we excel at understanding what other people think or believe. We even seem to be influenced by the belief of others in situations where it is irrelevant to our current tasks. Such altercentric interference has been proposed to reflect implicit belief processing. However, in which situations altercentric interference occurs and to what extent it is automatic or dependent on the relevance of the belief in context are open questions. To investigate this, we developed a novel task testing whether participants show an altercentric bias when searching for an object in a continuous search space (a 'sandbox'). Critically, another agent is present that holds either a true or a false belief about the object location, depending on condition. We predicted that participants' search for the object would deviate from its actual location in direction of where the agent believed the object to be. Further, we tested how this altercentric bias would interact with an explicit belief reasoning version of the task, where participants are asked where the agent would look for the object. In two large, preregistered studies (N = 113 and N = 157), we found evidence for an altercentric bias in participants' object search. Importantly, this bias was only present in participants who conducted the explicit before the implicit task and started the experiment with the false belief condition. These findings indicate that altercentric biases depend on the relevance of the other's belief in the context of the task, suggesting that spontaneous belief processing is not automatic but context dependent.