Modern research on social norms makes an important distinction between descriptive norms (how people commonly behave) and injunctive norms (what one is morally obligated to do). Here we propose that this distinction is far from clear in the cognition of social norms. In a first study, using the implicit association test, the concepts of "common" and "moral" were found to be strongly associated. Some implications of this automatic common-moral association were investigated in a subsequent series of experiments: Our participants tended to make explicit inferences from descriptive norms to injunctive norms and vice versa; they tended to mix up descriptive and injunctive concepts in recall tasks; and frequency information influenced participants' own moral judgments. We conclude by discussing how the common-moral association could play a role in the dynamics of social norms.