Some Properties of Skin Conductance and Potential

ABSTRACT SC and SP were measured simultaneously from opposite hands during a stress period and a subsequent prolonged relaxation in 19 S s. With the S s relaxed, toward the end of the session, simultaneous measures of SC and SP were taken between various combinations of two active and two drilled reference electrodes on both hands. It was found that SC measured with the external voltage connected in series‐adding with the endogenous SP (i.e., positive pole to the active electrode) was some 13 percent higher than when measured in reverse polarity. Supplementary experiment showed that this‘rectification effect’ could be entirely attributed to the effect of the endogenous potential. A method of estimating SC from SP readings with no external current source was shown to give results equivalent to values measured in the usual way. These and other findings support the claim that steady‐state electro‐dermal properties fit a simple model consisting of a variable voltage and a variable resistance in series. Within‐subject correlations of SC and SP were high for S s with low average SCs, lower for high‐SC S s who seemed less able to relax. The data suggest that SP may be an inverted‐U shaped function of arousal and perhaps that the‘beta process,’ which drives the tonic SP downward with increasing arousal, may begin to function at much lower levels of arousal for some S s than for others. Phasic responses obtained at the end of the session when some S s were apparently asleep suggest that, when S is drowsy or in light sleep, both the SCR and the SPR have lengthened and variable latencies, and the SPR is uniformly a large, negative going (alpha) response. Uniphasic beta SPRs were rather consistently obtained when the pre‐stimulus tonic SP was already high.