Fig. 1.

Standard waveforms for all three age groups. Event-related brain potentials (ERPs) evoked by the standard (p = .88) tones in the oddball sequence are displayed for each condition and age group. Waveforms for children are displayed at the Fz electrode (left column), where the obligatory responses have the largest signal to noise ratio, and are displayed where the signal is largest in adults, at Cz (right column). The dashed lines depict the waveforms in the Active conditions, softer sound (dashed purple line) when the deviant was the louder sound, and louder sound (dashed black line) when the deviant was the softer sound. The solid lines depict the waveforms in the Passive conditions: the softer standard (red line) when the deviant was louder; the louder standard (light blue) when the deviant was softer; and softer sound (green line) when frequency was deviant. The latency of the P1 component is marked with a gray bar, illustrating the significantly shorter latency with maturation. Note the difference in amplitude of the overall waveforms in adults compared to children, especially at this rapid (300 ms onset-to-onset) stimulus presentation rate. There is no frequency oddball condition for adults.