ISSN 0439-755X
CN 11-1911/B

›› 2009, Vol. 41 ›› Issue (04): 316-328.

### The Functionally Separation of P300 and CNV in Lie Detection

CUI Qian;ZHANG Qing-Lin;QIU Jiang;LIU Qiang;DU Xiu-Min;RUAN Xiao-Lin

1. Key Laboratory of Cognition and Personality (SWU), Ministry of Education, Chongqing 400715, China; School of psychology, Southwest University ,Chongqing 400715, China

• Received:2008-07-13 Revised:1900-01-01 Published:2009-04-30 Online:2009-04-30
• Contact: ZHANG Qing-Lin

Abstract: Some researches which have proved that the P300 and the CNV are effective indicators in lie detection, and they are affected by different factors. In the lie detection, the P300 is found to be closely related to stimulus attribute, while the CNV is only related to the response of a subject (deception or honesty). However, there is no research which induces the two ERPs synchronously in one experiment, and no any studies reveals the functional distinction of the two indicators in lie detection and further compares their consequences in lie-detection. Based on previous research, our study assumes that the P300 and the CNV are functionally different in lie-detection and they might reflect different cognitive phases in deception. In order to compare and explore the characteristics of the P300 and the CNV in lie-detection, this study induced “spontaneous deception” under the condition of a “murder game”, and combined GKT (guilt knowledge test) which was often used in the P300 lie-detection research with delayed-response paradigm which induced the CNV to design a new paradigm, so as to induce the two ERPs synchronously in lie-detection and separate them by controlling feedback.
There were 33 subjects who participated in this research. They were divided into two groups:
17 of them got feedbacks concerning the outcome of lie-detection while other 16 didn’t.This experiment included two steps. Subjects played a “murder game” before lie detection, and their event-related brain potentials (ERPs) were measured during the detection. We mainly analyzed the ERPs evoked by three kinds of stimuli.
Our result revealed a distinctive tendency between the P300 and the CVN in both groups. Whether there was feedback did not affect the amplitude of P300. In both of the two groups, the amplitude of P300 elicited by probe stimulus was significantly larger than that elicited by the irrelevant stimulus no matter whether feedback was acquirable. The P300 could detect lie effectively. In contrast, absence of feedback could affect the amplitude of the CNV. The amplitude of the CNV elicited by the probe stimulus was significantly larger when people got feedbacks than when they didn’t. The CNV could only detect lie effectively in the condition of having feedback. The data concerning lie-detection rates of the two indicators reflected that: the lie-detection rate of CNV elicited in feedback group was significantly larger than that in no-feedback group, which were 88.24% and 43.75% respectively; while the rates of the P300 elicited in the two groups were 70.6% and 75% , respectively.
The results revealed that the P300 and the CNV were separate on the function of cognitive process. The former was related to the cognitive process of stimulus in deception, while the latter was related to the processes such as response to deception and generating deceptive intention etc. In addition, the two indicators were separate concerning detection rate in different conditions. P300 could detect lie effectively in both conditions while the CNV could only be used as an available indicator of lie detection in the condition of getting having feedback.

Key words: Lie Detection, P300, CNV