Experiment 1: Grand-averaged event-related potentials (ERPs) (top row), difference waveforms (deviant-minus-standard) (middle row), and mastoid-referenced difference waveforms (bottom row) are shown for frequency deviants (left column) and intensity deviants (right column). Small-level deviants (F1 and I1) are denoted with a solid black line; medium-level deviants (F2 and I2) with a dashed black line, and large-level deviants (F3 and I3) with a dotted black line. The ERP response evoked by the standard tones is shown with a solid gray line (top row only). ERP components (N1, MMN, and P3a) are labeled.