3.5, SE = 0.09), F(1, 196) = 591.7, p < .0001. However, the Valence × Arousal interaction was significant for the valence ratings, F(1, 196) = 50.8, p < .0001; among high-arousal stimuli, positive pictures had higher valence ratings (M = 6.31, SE = 0.12) than negative pictures (M = 2.46, SE = 0.12), but this difference was not as pronounced for low-arousal stimuli (positive: M = 6.63, SE = 0.12; negative: M = 4.53, SE = 0.12). This outcome reflects an inherent property of the IAPS (P.J. Lang et al., 1999) and does not represent anything unusual about the stimuli selected for the present study. Because the Arousal × Valence interaction for valence ratings indicated that the valence manipulation was stronger for high-arousal pictures, we confined fMRI analyses of valence to the high-arousal condition only.
