Only 36 electrodes that represented 6 scalp regions were selected for the statistical analyses (see Fig. 2). The ERP data were analyzed by performing a linear mixed model of the Analysis of Variance (ANOVA) using the Statistical Analysis System (SAS, version 9.2) (SAS Institute Inc., NC 27513, USA). The values with ±4 standard deviations were considered as outliers and removed from the data before the analysis. The covariance structure used in the model was ‘Compound Symmetry’ which has a constant variance and constant covariance. The model included five factors as fixed effects: Valence (loss, gain), Amount (50¢, 10¢), Region (frontal, central, parietal, occipital, left-temporal, and right-temporal), Electrode (6 electrodes) as within-subjects factors, and Gender as a between-subjects factor. We treated electrodes as nested within region as we were interested in the “region” effects but not in the individual “electrode” effects. The pairwise comparisons for each main and interaction effect was calculated using the least means square values.
