Within-series physiological variations in the concealed information test

Abstract

Few studies have examined serial physiological variations during the concealed information test (CIT). This study analyzed both pre- and post-stimulus physiological measures from a CIT experiment under knowledgeable and unknowledgeable conditions. The physiological measures assessed in both the pre- and post- stimulus phases included skin conductance level (SCL), normalized pulse volume (NPV), and heart rate (HR). Moreover, skin conductance response (SCR) was assessed in the post-stimulus phase. The results showed that the post-stimulus SCL and SCR and post-stimulus NPV in the knowledgeable condition differed not only between the relevant and irrelevant CIT items but also between the irrelevant items that were presented before and after the relevant items. In both knowledgeable and unknowledgeable conditions, physiological activities and reactivity were higher at early positions than at late ones. However, in the knowledgeable conditions, serial positions of the relevant items modulated this tendency, such that physiological activities were maintained until the relevant item was presented and then declined afterwards. The practical and theoretical implications of these findings are discussed.