The use of the same pair of dry electrodes to record skin resistance and beat-by-beat heart rate

In situations of prolonged interrogation it is desirable to employ non-stressful methods of detecting responses to emotion-provoking questions. It is well known that changes in skin resistance and instantaneous heart rate are good indicators of emotional response. Changes in skin resistance and beat-by-beat heart rate, derived from the e.c.g., were obtained from the same pair of ‘dry’ silver electrodes applied to the finger tips. The electronic criteria to be satisfied for application of this technique are discussed and circuit diagrams are presented which permit construction of the equipment using low-cost solid-state circuitry. Typical records of changes in skin resistance and beat-by-beat heart rate, in response to lying in a number-guessing game, are presented to demonstrate the performance characteristics of the equipment.