Skin conductance rise time and amplitude discern between different degrees of emotional arousal induced by affective pictures presented on a computer screen

Skin Conductance Response (SCR) is a phasic change in electric conductivity of the skin, occurring either non-specifically, or in response to a stimulus (event-related, or ER-SCR). It has long been understood that ER-SCR amplitudes are greater when associated with unpleasant or high-arousal stimuli; however, the relationship between emotional valence and arousal to other ER-SCR measures such as ER-SCR latency (interval between stimulus onset and ER-SCR onset) and ER-SCR rise time (interval between ER-SCR onset and peak amplitude) is less well-established. Here, we presented 60 emotive pictures from IAPS and NAPS affective picture systems to a group of 100 young, healthy adults (50 male and 50 female) and recorded their electrodermal activity. We found that higher emotional arousal was associated with greater ER-SCR amplitudes and shorter ER-SCR rise times. Interestingly, while the increase in ER-SCR amplitudes was only observed for a subset of high-arousal stimuli (score 7-9 on a 9 point scale), the effect on ER-SCR rise times was more graded and particularly sensitive to the difference between low (score 1-3) and medium-arousal (score 4-6) categories. Next, we found that while ER-SCR amplitudes were greater in response to unpleasant stimuli (valence score 1-3 on a 9-point scale), none of the ER-SCR measures could distinguish between neutral (score 4-6) and positive stimuli (score 7-9). We suggest that the increase in ER-SCR amplitudes for unpleasant stimuli is primarily driven by the inherent association between unpleasantness and high arousal. In conclusion, we demonstrate that ER-SCR rise time conveys valuable information about emotional arousal and represents a useful complementary measure to ER-SCR amplitude in order to discern between multiple degrees of emotional arousal. Furthermore, this study confirms the cross-cultural validity of the IAPS and NAPS databases in a sample of young adult Czechs.