Electrodermal Activity (Eda) -- State-of-the-Art Measurement and Techniques for Parapsychological Purposes
Schmidt, Stefan, Walach, Harald, The Journal of Parapsychology
HARALD WALACH 
ABSTRACT: In most of the direct mental interactions with living systems (DMILS)/Remote Staring studies, electrodermal activity (EDA) is the only dependent variable. Therefore the quality of EDA recording is crucial. This is the reason why we studied EDA-related literature and contacted some of the leading psychophysiological labs in Germany to debate critical topics of the EDA measurement. We also checked the Methods section of all studies using FDA data published from 1995 to 1999 in the leading psychophysiological journals. In addition, we surveyed all DMILS/Remote Staring publications using EDA to find out whether parapsychologists adhere to these standards. In the first part of our paper we outline a current state-of-the-art FDA methodology. We also address various technical problems and describe sources for potential artifacts. In the second part we compare 24 DMILS/Remote Staring with a sample of 39 recent psychophysiological studies published in Psychophysiology and International Journal of Psychophysi ology. The analysis reveals that parapsychologists do not meet the current standards. There is not even one study conducted by parapsychologists which refers to psychophysiology's measurement standards published in 1981. Therefore, DMILS/Remote Staring data may either contain artifacts, or, on the other hand, may not detect the supposed effects. Although there is an ongoing trend of finding irregularities in FDA data of DMILS/Remote Staring experiments that can be related to different intentional conditions, there have not been any efforts to understand the results of EDA experiments or to address the origin of the irregularities in detail.
Since the early 1970s psychophysiological variables have been given growing importance in parapsychological research. Electrodermal activity (EDA), with its high lability, freely varying activity (Braud & Schlitz, 1991) and ability to map the orienting response (OR) has shown to be a promising outcome measure in experimental studies such as direct mental interaction with living systems (DMILS) and Remote Staring or presentiment experiments.
Therefore, some psychophysiologists are getting more and more interested in parapsychological research, and there is an advantageous exchange between those disciplines. But this exchange presupposes that the parapsychological community is willing to use EDA measurement, equipment and techniques that are state of the art from a psychophysiological point of view.
The psychophysiological community developed its standards for EDA measurement in the 1970s and published them in the beginning of the 1980s (Fowles et al., 1981; Lykken & Venables, 1971; Venables & Christie, 1980). In the 1990s, the fast progress in computer processing brought about a change in signal scoring and recording changing from polygraph and ruler to digital data recording and electronic analysis. This development enabled new possibilities of parametrization but left the measurement principles untouched.
In addition to using a technique that is also acceptable for researchers working in other disciplines than parapsychology, it is a required standard in every parapsychological publication to provide a detailed and clear description of the techniques and procedures which have been used. The reason for that is first to meet the scientific standard which in turn ensures a replication of that study with the information provided in the publication. Second, such description is necessary for future meta-analyses. Meta-analyses are becoming increasingly important because, in addition to the mean main effect size over a large body of studies, they provide detailed correlations between study characteristics and effect sizes (see e.g., Bem & Honorton, 1994; Honorton & Ferrari, 1989). For identifying study characteristics and applying quality ratings, detailed descriptions are necessary, even if they look very obvious. …