Research has shown that moral judgments depend on the capacity to engage in mental state reasoning. In this article, we will first review behavioral and neural evidence for the role of mental states (e.g., people's beliefs, desires, intentions) in judgments of right and wrong. Second, we will consider cases where mental states appear at first to matter less (i.e., when people assign moral blame for accidents and when explicit information about mental states is missing). Third, we will consider cases where mental states, in fact, matter less, specifically, in cases of “purity” violations (e.g., committing incest, consuming taboo foods). We will discuss how and why mental states do not matter equivalently across the multi‐dimensional space of morality. In the fourth section of this article, we will elaborate on the possibility that norms against harmful actions and norms against “impure” actions serve distinct functions – for regulating interpersonal interactions (i.e., harm) versus for protecting the self (i.e., purity). In the fifth and final section, we will speculate on possible differences in how we represent and reason about other people's mental states versus our own beliefs and intentions. In addressing these issues, we aim to provide insight into the complex structure and distinct functions of mental state reasoning and moral cognition. We conclude that mental state reasoning allows us to make sense of other moral agents in order to understand their past actions, to predict their future behavior, and to evaluate them as potential friends or foes.

How do people consider other minds during cooperation versus competition? Some accounts predict that theory of mind (ToM) is recruited more for cooperation versus competition or competition versus cooperation, whereas other accounts predict similar recruitment across these two contexts. The present fMRI study examined activity in brain regions for ToM (bilateral temporoparietal junction, precuneus, dorsomedial prefrontal cortex) across cooperative and competitive interactions with the same individual within the same paradigm. Although univariate analyses revealed that ToM regions overall were recruited similarly across interaction contexts, multivariate pattern analyses revealed that these regions nevertheless encoded information separating cooperation from competition. Specifically, ToM regions encoded differences between cooperation and competition when people believed the outcome was determined by their and their partner's choices but not when the computer determined the outcome. We propose that, when people are motivated to consider others' mental states, ToM regions encode different aspects of mental states during cooperation versus competition. Given the role of these regions for ToM, these findings reveal distinct patterns of social cognition for distinct motivational contexts.

Early in human development, children react negatively to receiving less than others, and only later do they show a similar aversion to receiving more. We tested whether theory of mind (ToM) can account for this developmental shift we see in middle childhood. We conducted a face-to-face fairness task that involved a ToM manipulation, measured individual differences in ToM, and collected parent-ratings of children’s empathy, a construct related to ToM. We find that greater ToM capacities lead to more rejections of unequal offers, regardless of the direction of inequality, demonstrating that children with greater ToM are more likely to engage in costly compliance with fairness norms. Moreover, drawing attention to mental states sufficiently elicits aversion to advantageous inequity in younger children. These findings contribute to our growing understanding that people’s concerns for fairness rely not just on their own thoughts and beliefs but on the thoughts, beliefs, and expectations of others.

While we may think about harm as primarily being about physical injury, harm can also take the form of negative psychological impact. Using functional magnetic resonance imaging, we examined the extent to which moral judgments of physical and psychological harms are processed similarly, focusing on brain regions implicated in mental state reasoning or theory of mind, a key cognitive process for moral judgment. First, univariate analyses reveal item-specific features that lead to greater recruitment of theory of mind regions for psychological harm versus physical harm. Second, multivariate pattern analyses reveal sensitivity to the psychological/physical distinction in two regions implicated in theory of mind: the right temporoparietal junction and the precuneus. Third, we find no reliable differences between neurotypical adults and adults with autism spectrum disorder with regard to neural activity related to theory of mind during moral evaluations of psychological and physical harm. Altogether, these results reveal neural sensitivity to the distinction between psychological harm and physical harm.

Although harm primarily elicits thoughts of physical injuries, harm can also take the form of negative psychological impact. Using functional magnetic resonance imaging (fMRI), we examined the extent to which moral judgments of physical and psychological harms are processed similarly, focusing on brain regions implicated in mental state reasoning or theory of mind, a key cognitive process for moral judgment. Univariate analyses reveal similar levels of theory of mind processing for psychological and physical harms, though multivariate pattern analyses (MVPA) reveal sensitivity to the psychological/physical distinction in two regions implicated in theory of mind: the right temporoparietal junction and the precuneus. Moreover, while there were no differences in neurotypical adults and adults with autism spectrum disorder with regard to neural activity related to theory of mind, there was a group difference in the recruitment of the anterior cingulate cortex for psychological versus physical harms. Altogether, these results reveal sensitivity within regions implicated in theory of mind to the physical / psychological distinction as well as neural processes that capture clinically relevant differences in evaluations of psychological harms versus physical harms.