3.4 Feedback P300s (a positivity peaking at 424 ms
corresponded to feedback-locked P300 at Pz, see Figure 6b)
Regarding feedback P300, another mixed 2 (stimulus type: probe vs.
irrelevant) by 2 (feedback type: success vs. failure) by 2 (group:
guilty vs. innocent) ANOVA was performed on the feedback-P300 component.
Results revealed a significant main effect of stimulus type, F (1, 58) = 39.63, p < 0.001,ηp2 = 0.41,
BFInclusion = 1.36 × 1010, revealing a
more positive feedback-P300 following feedback regarding the probe than
the irrelevant (7.30 ± 0.89 μV vs. 4.45 ± 0.73 μV). Notably, there was a
significant two-way interaction between stimulus type and group,F (1, 58) = 63.77, p < 0.001,ηp2 = 0.52,
BFInclusion = 1.52 × 108. Follow-up
tests indicated that the probe elicited a more positive feedback-P300
than the irrelevant did in the guilty group: 10.15 ± 1.26 μV vs. 3.70 ±
1.04 μV, F (1, 58) = 101.97, p < 0.001,ηp2 = 0.64,
BF10 = 5.61 × 105. However, among
innocent participants, there was no difference in the feedback-P300
between the probe and the irrelevant (4.44 ± 1.26 μV vs. 5.21 ± 1.04 μV,F (1,58) = 1.43, p = 0.24, BF01 = 0.33).
Other significant interactions were not found: stimulus × feedback:
(F (1, 58) = 0.06, p = 0.81,
BFExclusion = 4.29); feedback × group: (F (1, 58)
= 1.61, p = 0.21, BFExclusion = 1.34);stimulus × feedback × group interaction : (F (1, 58) = 0.006, p = 0.94, BFExclusion = 7.04).
For grand-averaged ERPs elicited by feedback stimuli, see Figure 2. For
grand-averaged ERPs and their scalp distributions elicited by feedback
stimuli, see Figures 5 and 7.