Reliability of psychophysiological assessment

In order to assess the reliability of psychophysiological recording, 15 subjects were assessed on multiple response measures (forehead EMG and forearm flexor EMG, heart rate, skin resistance level, hand surface temperature and cephalic vasomotor response), under multiple stimulus conditions (baseline, self-control, cognitive and physical Stressors), on multiple occasions (Days 1, 2, 8 and 28). Three forms of reliability coefficients were computed for each response measure: coefficients on absolute scores, coefficients on change scores from baseline to stressful conditions and coefficients on percent change from baseline. Only frontal EMG appeared to have consistently high absolute reliability coefficients, with hand surface temperature having high reliability if sessions are repeated within 1 week. Heart rate was less consistently reliable. Treating the responses as relative measures did not increase their reliability; indeed, hand surface temperature was completely unreliable when examined in this fashion. Implications of this study for behavioral medicine, biofeedback and anxiety-based disorders research, as well as Lang's tripartite response system model of fear and emotion, are discussed.