Study On P300-Based Implicit Lie Detection

There are generally two paradigms used in P300-based lie detection studies: two-stimulus and three-stimulus paradigm. The merits of two-stimulus paradigm are: smaller number of trials and high efficiency. However, one significant disadvantage of this paradigm is that the attentional level of participants is relatively lower compared to three-stimulus paradigm. Thus, the main aim of the current research is to improve the attention level in the two-stimulus paradigm and employed the updated paradigm to mock crime situation to investigate its validity and reliability.The current research has made a couple of revisions to the classic two-stimulus paradigm: 1, the stimuli were colored in red or blue; 2, participants should delay their responses to colors. Since there is no requirements that participants should make deceptive responses, so the updated lie detection paradigm is called an implicit lie detection technique. The principle underlying this paradigm is that when participants discriminate the color, they automatically process the stimulus' meanings; therefore a significant P300 is elicited. When the probe has evoked larger P300 than irrelevant, it could be inferred that the participants are aware of the stimuli's meaning.The research consists of two experiments: Experiment 1 has employed participants' own names as probe stimuli and strangers' names as irrelevants' stimuli; Experiment 2 has employed the mock crime scenario Here the stimuli are crime-relevant, served as probe, and crime-irrelevant stimuli, served as irrelevant.The main conclusions are:(1) There is no difference between color and stimuli type regarding reaction time, the stimuli could not be inferred from reaction time data;(2) This implicit paradigm could be used to detect concealed information, regardless the stimuli was personal information or mock crime information. P300 at Pz showed significant different between probe and irrelevant;(3) Different color does not influence the difference between probe and irrelevant regarding P300 amplitude;(4) The Pz site is an ideal area to detect information relative to Fz and Cz.