Research in the domain of cognitive science has tended to neglect emotions. In my thesis however, I take several steps to fill in this gap by looking at people’s representation of emotions, and its connection to other representations typically studied in cognitive science. Specifically, I argue that people have an intuitive theory of emotion that is causally intertwined with their understanding of the physical and social world broadly. This intuitive theory allows us to use observed emotional cues as a window, to recover unobserved information about the world. I study these abilities in both adults and children, to gain insight into the most fundamental representations supporting such abilities. I also use computational models to capture the hierarchical, causal structure of this intuitive theory of emotion. 

     I report evidence in three studies. In Study 1, I show that infants as young as 12-17 months can map diverse positive emotional vocalizations to their probable causes in the environment. In Study 2.1, I present that children can also recover rich mental state information from emotional expressions. When the valence of someone’s facial expression changes between anticipated and actual outcomes, children by age five gain insight into what she wants and believes about the world. Study 2.2 bridges theory of mind research, accounts of emotion attribution, and formal modeling, to provide a formal account of how people jointly infer beliefs and desires from emotions. Study 3 tests children’s understanding of the communicative role of emotional expressions. By seven, children can perform recursive mental state reasoning, using one person’s masked emotional expression to infer the mental states of another. 

     Altogether, these findings suggest that emotional cues provide a valuable entrée into the unseen world. Not only adults, but also children, can use others’ emotional expressions to infer both the external causes of those expressions and the internal mental states of other people. Although this intuitive theory of emotion may not necessarily mirror the actual processes of how emotions are generated, it supports accurate inferences much of time in people’s daily life, and it may be formed early in development. I see this work as bridging gaps across disciplines and helping advance the cognitive science of emotion understanding.