Abstract
The purpose of this study was to examine heart rate (HR) changes in detection of deception using the Guilty Knowledge Test (GKT) paradigm. The effects of verbal responses and the serial position of items on HR were investigated. Seventeen healthy adult men and women participated in the study. They participated in experiments with differing conditions. In a verbal condition, participants were asked to say “no” and to click the “mouse” after each item. In a non-verbal condition, they were requested just to click the “mouse” without giving an oral answer after each item. Every participant was given one of 6 items and subjected to a polygraph test under both conditions. Each participant was presented with 5 items at random in one set. Six sets of questions were carried out under both conditions. Each item was presented once in each set. The order of items was different for every set. The results showed a greater change in HR in the verbal experiment than in the non-verbal experiment. In both experiments, however, HR decreased more significantly 5-10 seconds after the onset of clicking in the case of critical items (CR) compared to noncritical items (nCR). The results indicated that verbal response did not undermine the accuracy of detection of deception, though verbal response could affect HR. In regard to the effect of the position of the items, the present study indicated that serial position of items could affect HR because HR decreased gradually through out the set.
