Psychological Correlates of Nonspecific Electrodermal Responses

Abstract

Spontaneous fluctuations in electrodermal responses are known as nonspecific electrodermal responses (NS.EDRs). The use of NS.EDRs as a tool in applied psychophysiological research has resulted in a variety of publications. NS.EDRs are examined separately as associated with the (as a biomarker of) levels of anxiety. The aim of this study was to compare changes (in terms of amplitude, frequency and time components) in NS.EDRs at two different (pre and post of an external stimulus) resting phases. NS.EDRs (nonspecific skin conductance responses (NS.SCRs), nonspecific skin potential responses (NS.SPRs), and nonspecific skin susceptance responses (NS.SSRs)) were recorded from 50 apparently healthy volunteers simultaneously at the same skin area. They were scored as NS.SCRs and NS.SSRs for changes greater than 0.02 μS and NS.SPRs greater than 0.02 mV. It was found that NS.EDRs, in particular NS.SCRs and NS.SPRs, were significantly changed in the second resting period, following the specific stimulus. More specifically, the amplitude of NS.EDRs were significantly decreased for NS.SCRs (p<0.001) and for NS.SPRs (p<0.005), but NS.SSRs remained stable. Moreover, the rise time of NS.SCRs was decreased in the second resting time. Furthermore, the frequency of responses was also changed. The computed NS.EDRs, in particular NS.SCRs and NS.SPRs could be of psychological interest and be used to study the electrodermal responses in detail. NS.SSRs were found to be robust with respect to nonspecific stimuli at various relaxation periods and their role was found to be less important in analysis of NS.EDRs in comparison to NS.SCRs and NS.SPRs at low frequency (20 Hz AC current). This should be considered in analysis of NS.EDRs. The computed NS.EDRs, especially NS.SCRs and NS.SPRs may be used as a useful measure of arousal due to their fast response and sensitivity to nonspecific stimuli and may also be used in assessment of individual differences.

Keywords: EDA; Electrodermal activity; nonspecific electrodermal responses; skin conductance responses; skin potential responses; specific electrodermal responses.

Fig.1

Time schedule of the experiment.

Fig. 2

Distribution of NS.SCRs frequency for the total sample (n = 50): (A) first resting period, and (B) second resting period.

Fig. 3

Distribution of NS.SPRs-frequency for the total sample (n = 50): (A) first resting period, and (B) second resting period.

Fig. 4

Box-plot with medians, quartiles and the min and max as whiskers shows average value of NS.SCRs_Amp at relaxation periods for all participants (n=50). **p<0.001

Fig. 5

Box-plot with medians, quartiles and the min and max as whiskers shows average value of NS.SPRs_Amp at relaxation periods for all participants (n=50). **p<0.005

Fig. 6

Box-plot with medians, quartiles and the min and max as whiskers shows average value of NS.SCRs_Tris at relaxation periods for all participants (n=50). **p<0.005

Fig. 7

Box-plot with medians, quartiles and the min and max as whiskers shows average value of SPRET at relaxation periods for all participants (n=50). **p<0.001

Fig. 8

SCRs, SSRs, and SPRs recorded from a test subjects, demonstrating stable waveform of SSRs in response to nonspecific stimuli.