The age group × gender effect showed that younger male subjects manifested significantly higher P3 amplitude, but this pattern (younger > older) was not statistically significant in female subjects. In terms of gender differences across scalp regions, the younger age group showed significantly higher P3 amplitude in parietal and occipital regions while the older group showed significant increases in the frontal region as revealed by age group × region effect. Overall, younger subjects displayed significantly higher P3 amplitude than older subjects as shown by the main effect of age group. Comparisons between age groups across other factors (see Fig. 4, panels C1–C2) confirm that this pattern (younger > older) is true in several subgroups except for the anterior regions in older females, where the opposite pattern (older > younger) was observed.
