Infants' responsiveness to others' affective expressions was investigated in the context of a peekaboo game. Forty 4-month-olds participated in a peekaboo game in which the typical happy/surprised expression was systematically replaced with a different emotion, depending on group assignment. Infants viewed three typical peekaboo trials followed by a change (anger, fear, or sadness) or no-change (happiness/surprise) trial, repeated over two blocks. Infants' looking time and affective responsiveness were measured. Results revealed differential patterns of visual attention and affective responsiveness to each emotion. These results underscore the importance of contextual information for facilitating recognition of emotion expressions as well as the efficacy of using converging measures to assess such understanding. Infants as young as 4 months appear to discriminate and respond in meaningful ways to others' emotion expressions.