Study On Lie Detection With The Combination Of P300 And CNV

ERP (Event related potentials) has been widely acknowledged in psychology, especially in the field of lie detection. But most research still detected crimes by single potential, for example, with P300, researchers can detect the special information on crimes. But, there are some people who witness crime in some criminal cases. The witnesses also have information about the crime even though they did not conduct a crime. Thus, they may not be classified into the innocent groups because of their memories of the crime. If other indicators could be induced in lie detection, the accuracy of detection will be improved.In our study, P300 and CNV have been integrated to research the EEG of two different group in delay feedback paradigm based GKT. In experiment 1, participants were randomly and assigned to two groups (guilty group, witness group), and then they were respectively required to make classification among three types of word stimulus (Probe, Target, Irrelevant). Results showed that two groups had the same trends on the amplitude of P300 but not on the average amplitude of CNV, we could make a clear distinguish between two groups. To further verify the stability of the paradigm, in our experiment 2, participants were presented pictorial stimulus instead of text stimulus, and we found that results had the same trends. Also, the Probe stimulus was significantly greater than the Irrelevant stimulus in the more there were more electrode, no matter the amplitude of P300 or the average amplitude of CNV.According to these experiments, we can make some conclusions:First, we can use P300 and CNV to make detection in the delay feedback paradigm based GKT. Second, P300 and CNV have different features, P300 is related to guilty knowledge-related information, participants will be regards as crime as long as they have seen something about crime. CNV is related to the process of lying including the process of suppressing the real reaction, the process of execution errors related conflict and so on. Third, P300 and CNV are complementary methods in witness detection, and can avoid a high false alarm rate. Finally, a pictorial cue is more effective than a word in some electrodes. The Probe stimulus is significantly greater than the Irrelevant stimulus in Cz and Fz when use word stimulus. Cz, Fz and Pz are significant when we use pictorial stimulus.