We demonstrated unconscious learning of task-irrelevant perceptual regularities in a Serial Reaction Time (SRT) task in both visual and auditory domains. Participants were required to respond to different letters ('F' or 'J', experiment 1) or syllables ('can' or 'you', experiment 2) which occurred in random order. Unbeknownst to participants, the color (red, green, blue or yellow) of the two le...