We explored whether 15-month-olds expect another person's emotional disposition to be stable across social situations. In three observation trials, infants watched two adults interact. Half the infants saw one of the adults (“Emoter”) respond negatively to the other adult's actions (Anger group); half saw the Emoter respond neutrally to the same actions (Neutral group). After a change in social context, infants participated in novel tasks with the (now-neutral) Emoter. Infants in the Anger group were significantly more likely to relinquish desirable toys to the Emoter. We hypothesize that, in the initial observation trials, infants learned that the Emoter was “anger-prone” and expected her to get angry again in a new social situation. Consequently, infants readily gave the Emoter what she wanted. These findings reveal three key features of infants' affective cognition: (1) infants track adults' emotional history across encounters; (2) infants learn from observing how people interact with others and use this to form expectations about how these people will treat them; and (3) more speculatively, infants use appeasement to cope with social threat. We hypothesize that infants form “trait-like” attributions about people's emotional dispositions and use this to formulate adaptive responses to adults in novel social contexts.