In the mood to get over yourself: mood affects theory-of-mind use.

Understanding others' behavior often involves attributing mental states to them by using one's "theory of mind." We argue that using theory of mind to recognize differences between one's own perspective and another's perspective is a deliberate process of inference that may be influenced by incidental mood. Because sadness is associated with more systematic and deliberate processing whereas happiness is associated with more heuristic processing, we predicted that theory-of-mind use would be facilitated by sadness compared with happiness. Two experiments supported this prediction, demonstrating that participants were more likely to utilize knowledge about others to make inferences about their mental states when they were induced to feel sad than when they were induced to feel happy. These results provide both theoretical insight into the psychological mechanisms that govern theory of mind as well as practical insight into a common source of variability in its use.