Research in the Mind-Emotion Development Lab focuses on developmental changes in knowledge about people in terms of their inner, mental lives–what a person desires, intends, believes, thinks about, and feels emotionally. We investigate age-related changes and individual differences in children’s and adults’ emotion understanding, theory of mind, moral cognition, and past-to-future reasoning. This has included studies on children’s and adults’ understanding of emotions and decisions caused by being reminded about past experiences or by anticipating future events, reasoning about causes of fear and worry and strategies that can help alleviate negative emotions, beliefs about the effects of emotions on thinking, knowledge about the influence of optimistic versus pessimistic thoughts and expectations on emotions and decisions, reasoning about mental diversity and common ground in interpretation, and heuristics and biases in social categorization. We further conduct research that bridges theory of mind, moral reasoning, and intergroup relations, including studies on beliefs about emotions, decisions, and obligation in willpower, transgression, and altruistic helping contexts. Sources of individual differences include worry and anxiety, working memory, inhibitory control, visual attention biases, reasoning about probability and uncertainty, family composition (especially siblings), and attachment.