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UBC Theses and Dissertations

The effect of electrode size on electrodermal measurement Mahon, Mary L.


The effect of the size of electrode contact area on skin conductance (SC) measures has not been clearly resolved. On the basis of the anatomical structure and current electrodermal models of the skin, it is expected that the relationship between SC and the size of electrode contact area will be linear such that increases in contact area will produce corresponding increases in SC. This hypothesis was not supported in the most recent study investigating this relationship (Mitchell & Venables, 1981). However, methodological problems existed with this study which may have contributed to these counterintuitive results. The present study reexamined this relationship while exerting careful experimental control. Forty-eight, right-handed male subjects were randomly assigned to six groups of eight subjects each. Six pairs of electrodes with different size contact areas were placed on six locations on the hands. A' 6 (group) X 6 (size of electrode) latin square design was used, with location of electrode placement as the latinized variable. Each group had the electrodes placed on one of six possible location-size combinations. The latinized variable, location of electrode placement, was further broken down in a 2 (hand) X 3 (area on hand) factorial arrangement. Dependent measures were tonic SC level, and the phasic SC amplitude, latency, rise time, and recovery half-time of responses elicited by a series of loud tones, half-time. Differences in tonic and phasic reactivity at the different electrode placement locations were also examined. The results indicated a significant linear relationship between size of electrode and both tonic and phasic activity. Latency measures were not affected by electrode size; however, rise time and recovery half-time were. No differences in reactivity were found between the right and left hands. Differences were found, however, among the three locations on the hands for both tonic and phasic activity. The observed linear relationship between electrode size and SC supports current popular models of electrodermal activity and has implications for the comparison of results from studies in which different electrode sizes are used.

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