3.2 Recognition P300s (a positivity peaking at 384 ms
corresponded to recognition-related P300 at Pz, see Figure 3b)
For recognition-P300, we conducted a two-way 2 (within-subject:
probe vs. irrelevant) by 2 (between-subject: guilty vs. innocent) mixed
ANOVA on the P300 amplitude. The results showed a significant main
effect of stimulus type, F (1, 58) = 64.25, p <
0.001, ηp2 = 0.53,
BFInclusion = 6.34 × 1010, with a
larger P300 elicited by the probe than by the irrelevant (7.17 ± 0.80 μV
vs. 3.79 ± 0.60 μV). There was also a significant main effect of group:F (1, 58) = 9.87, p = 0.003,ηp2 = 0.15,
BFInclusion = 1.50 × 107, indicating
that the P300 in the guilty group was significantly larger than in the
innocent group (7.60 ± 0.95 μV vs. 3.36 ± 0.95 μV). As expected, there
was a significant stimulus type × group interaction: F (1, 58) =
49.37, p < 0.001,ηp2 = 0.46,
BFInclusion = 5.85 × 106. Follow-up
tests showed that among guilty participants, the probe elicited
significantly larger P300 than the irrelevant (10.76 ± 1.13 μV vs. 4.43
± 0.85 μV, F (1, 58) = 113.13, p < 0.001,ηp2 = 0.66,
BF10 = 3.96 × 106). In contrast, no
differences in P300 amplitude were found between the probe and
irrelevant for innocent participants (3.57 ± 1.13 μV vs. 3.15 ± 0.85 μV,F (1, 58) = 0.49, p = 0.49, BF01 = 2.91).
For grand-averaged ERPs and their scalp distributions that are
time-locked to CIT stimuli, see Figures 2 and 4 .