Separate analyses of the stimulus category for the time windows revealed no effects for s1 and s2 ( p > 0.10), and highly significant effects for s3, F (2,84) = 5.76, p = 0.006, η 2 = 0.12, s4, F (2,84) = 9.05, p < 0.001, η 2 = 0.18, and s5, F (2,84) = 9.40, p < 0.001, η 2 = 0.18, after stimulus onset (see also Figure 3A ).
No differences between reactions to neutral and unpleasant pictures can be reported, which might indicate a lowered sensitivity of FR Valence in the detection of unpleasant facial expression or a negative trend for neutral responses.
While FR Valence did not show a significant correlation with valence ratings of unpleasant pictures, FR Arousal showed at least a marginally significant enhancement for unpleasant compared to neutral or pleasant pictures.