Changes in the palmar sweat index during mental arithmetic

Abstract

This study investigated the influence of activation on the number of active sweat glands (palmar sweat index, PSI), as assessed by the plastic impression method. Subjects were 50 male students, assigned to two groups. The experiment involved 5 phases: an initial adaptation for 6 min in both groups (Phase I), 3 relaxation periods for 10 min (Phases II, IV and V in Group 1, Phases II, III and V in Group 2), and 10 min of mental arithmetic (Phase III in Group 1, Phase IV in Group 2). Prints were taken every 2.5 min from the left middle and forefinger, and skin conductance level (SCL), number of spontaneous fluctuations (SF) and heart rate (HR) were recorded for the corresponding intervals. PSI rose significantly during activation conditions and decreased afterwards. Accordingly, during Phase III values were higher in Group 1, whereas during Phase IV they were higher in Group 2. Decrease of PSI during the first measurements indicated that subjects probably react to the assessment procedure itself and that interpretable baseline values can only be obtained after several initial assessments. Correlations between PSI and electrodermal variables proved to be high within subjects, whereas correlations across subjects were lower.