Eye movements in Sally-Anne false-belief tasks appear to reflect the ability to implicitly monitor the mental states of other individuals (theory of mind, or ToM). It has recently been proposed that an early-developing, efficient, and automatically operating ToM system subserves this ability. Surprisingly absent from the literature, however, is an empirical test of the influence of domain-general executive processing resources on this implicit ToM system. In the study reported here, a dual-task method was employed to investigate the impact of executive load on eye movements in an implicit Sally-Anne false-belief task. Under no-load conditions, adult participants displayed eye movement behavior consistent with implicit belief processing, whereas evidence for belief processing was absent for participants under cognitive load. These findings indicate that the cognitive system responsible for implicitly tracking beliefs draws at least minimally on executive processing resources. Thus, even the most low-level processing of beliefs appears to reflect a capacity-limited operation.

The ability to attribute mental states to others is crucial for social competency. To assess mentalizing abilities, in false-belief tasks participants attempt to identify an actor's belief about an object's location as opposed to the object's actual location. Passing this test on explicit measures is typically achieved by 4 years of age, but recent eye movement studies reveal registration of others' beliefs by 7 to 15 months. Consequently, a 2-path mentalizing system has been proposed, consisting of a late developing, cognitively demanding component and an early developing, implicit/automatic component. To date, investigations on the implicit system have been based on single-trial experiments only or have not examined how it operates across time. In addition, no study has examined the extent to which participants are conscious of the belief states of others during these tasks. Thus, the existence of a distinct implicit mentalizing system is yet to be demonstrated definitively. Here we show that adults engaged in a primary unrelated task display eye movement patterns consistent with mental state attributions across a sustained temporal period. Debriefing supported the hypothesis that this mentalizing was implicit. It appears there indeed exists a distinct implicit mental state attribution system.

There is now considerable evidence that neurotypical individuals track the internal cognitions of others, even in the absence of instructions to do so. This finding has prompted the suggestion that humans possess an implicit mental state tracking system (implicit Theory of Mind, ToM) that exists alongside a system that allows the deliberate and explicit analysis of the mental states of others (explicit ToM). Here we evaluate the evidence for this hypothesis and assess the extent to which implicit and explicit ToM operations are distinct. We review evidence showing that adults can indeed engage in ToM processing even without being conscious of doing so. However, at the same time, there is evidence that explicit and implicit ToM operations share some functional features, including drawing on executive resources. Based on the available evidence, we propose that implicit and explicit ToM operations overlap and should only be considered partially distinct.