ERP data
As shown in Figure 3, the two-way repeated-measure ANOVA for LPP amplitude demonstrated a significant main effect of price frame, F(2, 56) = 4.220, p = 0.020, ηp2 = 0.131, and electrode, F(2, 56) = 56.792, p = 0.000, ηp2 = 0.670. The LPP amplitude elicited by ZP (M = 5.627 μV, S.E. = 0.696) was more positive than that by NP (M = 4.730 μV, S.E. = 0.725, p = 0.013). But similar to the behavioral results, there was neither statistically significant difference of LPP amplitudes between ZP and LP (M = 4.979 μV, S.E. = 0.687, p = 0.279), nor between NP and LP (p = 1.000). Furthermore, the LPP amplitudes at Cz (M = 2.687 μV, S.E. = 0.652), CPz (M = 5.448 μV, S.E. = 0.724), and Pz (M = 7.202 μV, S.E. = 0.783) differed from each other (ps < 0.05). However, the interaction between price frame and electrode was not significant, F(4, 112) = 1.932, p = 0.110, ηp2 = 0.065.
Figure 3  ERP results. Grand-averaged ERP waveforms from three central electrodes (Cz, CPZ, and Pz) time-locked to the onset of price stimulus. The gray rectangles denote the time window for LPP analysis. Positive voltage is plotted downwards.