In this article, we examine whether artificial grammar learning is implicit according to a subjective criterion of awareness based on confidence ratings. In four experiments, participants discriminated between grammatical and ungrammatical sequences in both the same (Experiment 1) and a novel (Experiments 2-4) vocabulary and indicated their confidence in each decision. Replicating earlier studies, confidence judgments reported on a continuous scale (50%-100%) were only weakly related to accuracy, suggesting that learning was implicit. In contrast, confidence judgments reported on a binary scale (high vs. low) revealed that confidence was related to accuracy. We show that participants are better able to place their phenomenal states on a binary scale, as compared with a continuous scale.