Social interactions are heavily norm-based and these norms need to be learned. For this, the emotional reactions of other's in response to a norm transgression can serve as signals. We were able to show that when a group responds with anger to a norm transgressing behaviour, participants were better able to correctly infer the norm than when the group responded with sadness or emotional neutrality. We further tested a process-model showing that this inference is based on the participants' understanding of the groups' appraisals of the behaviour. That is, participants who were able to reverse engineer the underlying appraisal of norm-incompatibility from the emotion expressions inferred the norm more readily. Humans as a social species, require efficient means to quickly adapt to new situations and to perform flawlessly in social contexts. Emotion information is one of the instruments that can be used in this quest.