A Guide to Cleaner Electrodermal Activity Measurements
Biofeedback ÓAssociation for Applied Psychophysiology & Biofeedback Volume 44, Issue 2, pp. 90–100 www.aapb.org DOI: 10.5298/1081-5937-44.2.01 SPECIAL ISSUE A Guide to Cleaner Electrodermal Activity Measurements Fredric Shaffer, PhD, BCB,1 Didier Combatalade, DC,2 Erik Peper, PhD, BCB,3 and Zachary M. Meehan1 1Truman State University, Center for Applied Psychophysiology, Kirksville, MO; 2Thought Technology Ltd., Montreal, QC, Canada; 3San Francisco State University, San Francisco, CA Keywords: artifact, biofeedback, electrodermal activity, tracking test Valid electrodermal measurements ensure the integrity of The skin contains apocrine and eccrine sweat glands (see client assessment and biofeedback training. Accurate Figure 2). Apocrine sweat glands usually open into hair measurements require understanding of the signal and follicles and are mainly distributed in the armpits and potential artifacts (sources of contamination) and develop- genital region. These sweat glands can expel sweat from ing ‘‘bulletproof procedures.’’ Peper, Shaffer, and Lin have their tubules and produce the odor of sweat. Although recommended the following guidelines for ensuring accu- researchers can measure EDA from the armpits and genital rate psychophysiological monitoring: (a) understand the regions, it is seldom done. physiological mechanisms that generate the signal, (b) Eccrine sweat glands are distributed across the body, always record and inspect the raw signal because this will except for areas such as the lip margins, outer ear, clitoris, allow you to identify artifact, (c) question whether and glans penis. They are densest on the palms (palmar displayed values make sense (e.g., skin conductance levels surface) and soles of the feet (plantar surface). A square l 2 that rapidly fluctuate, exceed 40 S/cm , or fall below 1 inch of palmar surface may contain about 3,000 sweat lS/cm2 should be suspect in a client who is sitting quietly), glands (Jacob & Francone, 1970).
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