[Frequency and mean amplitude of spontaneous electrodermal fluctuations are not interchangeable indicators of psychological processes].

The study was concerned with the question of whether the frequency and the mean amplitude of spontaneous electrodermal fluctuations convey the same information about mental processes. In order to examine this, the content and the personal relevance of induced imaginations was varied experimentally. The experimental manipulations followed a 2 x 2 factorial design for independent groups (content of cells: 24 subjects each). Changes in electrodermal activity were measured as differences between the imagination and a resting phase. Results revealed that the two variables are not exchangeable indicators of mental processes. Although the two variables correlated significantly, they responded differently to the experimental manipulations. The imagination of death-related contents increased the frequency of spontaneous electrodermal fluctuations more than the imagination of neutral contents. High personal relevance enhanced the mean amplitude of these spontaneous fluctuations regardless of the imagined content. Therefore it was concluded that the two variables have something in common but, on the whole, do not depend on identical factors. Frequency of spontaneous electrodermal fluctuations seems to be a reflection of covert orienting processes, whereas their mean amplitude seems to reflect the activity of an appraisal system incorporating goals and past experiences. However, both variables, seem to be, in the same way, dependent on a kind of basal activation or vigilance.