• Korean Journal of Culture and Social Issue
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• v.14 no.4
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• pp.103-117
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• 2008

The polygraph test administered by the Korean Prosecutors Office for crime investigations customarily uses the score of -12 as the cutoff point separating the subjects who lie from those who tell the truth. The criterion used by the KPO is different from the one (-13) suggested by Backster (1963) who invented the particular method for lie detection. Based on the signal detection theory applied to the real polygraph test data obtained from real crime suspects by the KPO, the present study identified the score of -8 as an optimal criterion resulting in the highest overall accuracy of the polygraph test. The classification of the subjects with the score of -8 as the criterion resulted in the highest accuracy (83.17%) compared with the accuracies of classifications with the Backster's criterion (76.24%) and the KPO's criterion (80.20%). However, the new criterion was also found to result in more false-positive cases. Based on the results from the present study, it was recommended to use the score of -8 as the criterion when the overall accuracy is important but the score of -12 or -13 when avoiding false-positive is more important than securing the overall accuracy.

• Science of Emotion and Sensibility
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• v.12 no.4
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• pp.557-564
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• 2009

For scoring polygraph charts, the Prosecutors' Office of the Republic of Korea uses a consistency criterion in which an elevated signal on one physiological channel is scored as a deceptive response only if the signal is also elevated on other channels. In the current study, the effects of this scoring criterion on reliability and accuracy (validity) of polygraph scores were assessed. Polygraph tests on 26 suspects were evaluated twice by the same examiners. The examiners used the consistency criterion in the first evaluation. In the second evaluation, the examiners were prevented from using the criterion; the signals from each physiological channel were separated and randomly arranged before they were rescored by the same examiner. Reliability was assessed by the variation among the scores for each suspect. Accuracy was assessed by establishing a standard, based on a Latent Class Analysis model, using the results of polygraph tests on each of 182 additional suspects. Reliability and accuracy were both improved by the use of the consistency criterion which therefore was recommended.

• Convergence Security Journal
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• v.15 no.3_1
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• pp.41-51
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• 2015

Human have more complicate and skilled ability for lying even cheat ourself. It is not easy to cheat unconscious things like sweat, eyes, or voice, but if some one cheat own self, he can cheat every of that. Lie is one of the way to spread our gene and our instinct make a lie. Every living organism even bacteria or virus use similar trick to survive. In human body, there are more complicate and profound mechanism for lying like breathe, sweat, eyes, face or voice. We can control some of that and make a fake, but it can't be perfect. Human also called 'Homo Fallax' cause we have a language and skill to lie with it. In present, we can detect lie with polygraph, but it has few weakness. So we try to use Vibraimage technology for resolve it. In this paper, we describe how to use Vibraimage for lie detection and the research history.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2008.10a
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• pp.50-53
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• 2008

본 연구에서는 목표자극을 포함한 P300 숨긴 정보 검사와 목표자극을 제거한 P300 숨긴 정보 검사의 정확도를 비교하였다. 목표자극을 제거한 경우에는 피검사자의 주의를 검사상황에 집중하도록 하기 위하여, 1) 검사자극이 속한 범주에 대한 판단을 하도록 하거나, 2) 검사자극이 제시된 지 1.5초 후에 재인검사를 실시하였다. 16명의 피검사자에게 반복측정 설계를 이용하여 실험한 결과, 세조건 모두에서 에서 관련자극의 P300이 무관련자극의 P300보다 통계적으로 유의하게 큰 것으로 나타났다. 부트스트랩 방법을 이용한 개인별 판단 결과, 세 자극 방안의 정확도가 93.8%로 가장 높은 것으로 나타났으며 재인검사를 이용한 두 자극 방안의 정확도는 81.3%였으며, 범주판단을 이용한 두 자극 방안의 정확도가 62.5%로 가장 낮았다.

• Korean Journal of Forensic Psychology
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• v.11 no.1
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• pp.89-115
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• 2020

Traditional deception detection methods had examined the difference of one's autonomic physiological responses through asking crime-related and crime-unrelated questions. There has been a continuing controversy regarding the accuracy and validity of the test, and thus, many researchers were motivated to explore and develop alternative efficient methods of detection in which one of them is known as P300-based Complex Trial Protocol (CTP). The P300-based CTP detects deception through comparing the P300 amplitudes between probe and irrelevant stimuli and is known as a counterstrategy of countermeasures. However, many previous studies have used countermeasures created from Rosenfeld et al.'s work (2008). The present study initially conducted a survey asking open-ended questions about the countermeasure use to acquire participant-oriented countermeasures for the main experiment. Then, the study aimed to evaluate whether the CTP can accurately detect deception even in the use of survey-based countermeasures. We firstly selected a set of participant-oriented countermeasures through survey questions. Then, a total of 50 participants were divided into three groups (innocent, guilty, and countermeasures) and performed the CTP. Those assigned to the countermeasures group covertly performed mental countermeasures during the CTP. The results of P300 amplitude analysis revealed that the guilty group's P300 amplitude of probe stimuli was significantly larger than that of irrelevant stimuli. Countermeasures group also had a significantly larger P300 amplitude for probe stimuli compared to irrelevant stimuli, even in the use of countermeasures. The results of bootstrapped amplitude difference (BAD) showed a detection accuracy rate of 81.25%, 82.35%, 82.35% for the innocent, guilty, and countermeasures groups, respectively. These findings demonstrate that the CTP can obtain a high detection rate in participant-oriented countermeasures and suggest the potential use of the CTP in the field.

• Science of Emotion and Sensibility
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• v.20 no.3
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• pp.109-118
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• 2017

This study examined the effects of button response to probe and irrelevant stimuli on P300 amplitude and lie detection rate in P300-based concealed information test. Participants underwent the P300-based concealed information test (P300 CIT) in two conditions. In one button condition participants were instructed to press the left mouse button only when the target was present. In two button condition, they were asked to press the left mouse button for target and right button for non-target. The results showed that the response time to target stimulus was not significantly different between the two conditions, and the response time to the probe stimulus was significantly longer than the irrelevant stimulus. The P300 amplitudes for the probe and irrelevant stimulus were all smaller in one button condition compared to two button condition. However, the P300 amplitude difference between the probe stimulus and the irrelevant stimulus did not show a significant difference in the two experimental conditions, and the lie detection rate did not differ significantly between the two conditions. Based on these findings, the effect of button response on P300 CIT with a short inter-stimulus interval was discussed.

• Science of Emotion and Sensibility
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• v.21 no.3
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• pp.61-72
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• 2018

Items related to a crime that are known only to criminals and investigators can be used in the concealed information test (CIT) to assess whether the suspect is guilty of the offense. However, in many cases wherein the suspect is exposed to information about the crime, the CIT cannot be used. Although the perpetrator's memories about the details of the crime are episodic, the memories of a suspect who has inadvertently discovered the details of the crime are more likely to be semantic. The retrieval of episodic memories is associated with theta wave activity, whereas that of semantic memories is associated with alpha wave activity. Therefore, these aspects of memory retrieval can be useful in identifying the perpetrator of the crime. In this study, P300-based CITs were conducted in a guilty participant in a mock crime and an innocent participant who has been given information about the simulated offense. The results demonstrate that the difference in P300 amplitudes between the probe and the irrelevant stimulus did not differ between the guilty and innocent conditions. As expected, the lower theta band power (4-6 Hz) was higher in the probe than in the irrelevant stimulus in the guilty condition, but there was no difference in the innocent condition. Conversely, the upper alpha band power (8-10 Hz) was lower in the probe than in the irrelevant stimulus in the innocent condition, but there was no difference in the guilty condition. The possibility of using theta and alpha band powers in lie detection is discussed.

• Korean Journal of Forensic Psychology
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• v.11 no.2
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• pp.173-190
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• 2020

The purpose of this study is to verify whether it is possible for participants to discriminate between innocent and guilty suspects when they are exposed to criminal information utilizing an autobiographical implicit association test (aIAT). A total of 49 college students were randomly assigned to guilty group, innocent-aware group, or innocent-unaware group. Participants performed an aIAT to detect suspects after performing either mock crime or control task. It was verified that innocent suspect and guilty suspect exposed with crime information could be distinguished through D-score and reaction time, converted to symbolize strength of the association between guilty sentences, innocent sentences, and truth sentences. As a result of the analysis, guilty group showed significantly higher D-score than both innocent-aware group and innocent-unaware group. guilty group also showed faster response time in true-guilty condition than true-innocent condition. This shows that the association of true-guilty conditions is stronger than that of true-innocent conditions. On the other hand, the innocent-aware group showed a faster response time in the true-innocent condition than the true-guilty condition, and innocent-unaware group showed no significant difference between the two conditions. Through this, it was confirmed that innocent suspects exposed to criminal information can be discriminated according to the aIAT pattern, which has a faster reaction rate to the truth and innocence union than the guilty group. This study confirmed that suspects exposed to criminal information can be effectively discriminated using aIAT, and further suggests the usefulness and potential of aIAT in the field of lie detection.

• Science of Emotion and Sensibility
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• v.24 no.2
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• pp.3-12
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• 2021

Most researchers have experimentally evaluated the detection efficiency of reaction time-based concealed information tests (RT CIT). In experimental studies, two experimental paradigms have been mainly used to create a lying situation, mock-crime paradigm and personal-item paradigm. This study is aimed at testing the detection efficiency of RT CIT for the one that could be estimated as the same as the other, regardless of the experimental paradigms. In study 1, it was tested whether the effect size of RT CIT was different in the two experimental paradigms through meta-analysis. As a result of the meta-analysis of 39 studies, the effect size (Hedges'g = 1.330) of the mock-crime paradigm was slightly larger than that (Hedges'g = 1.145) of the personal-item paradigm, but no statistically significant difference was found. Study 2 was an experimental study using both the mock-crime and personal-item paradigms, it was conducted to determine whether the detection efficiency of RT CIT differs in the two experimental paradigms. As a result of ANOVA, it was found that the RT differences between the probe and irrelevant stimuli were not significant in the two experimental paradigms. In the experimental study, the effect size (Cohen's d) of the mock-crime and personal-item paradigms were 1.638 and 1.535, respectively. In the discussion section, the reason of the detection efficiency of RT CIT not affected by the experimental paradigms was discussed.

• Science of Emotion and Sensibility
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• v.13 no.3
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• pp.541-550
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• 2010

The present study examined whether the physical similarity of test stimuli affects P300 amplitude and detection accuracy for the P300-based concealed information test (P300 CIT). As the participant pretended suffering from memory impairment by an accident, own name was used as a concealed information to be probed by the P300 CIT in which the participant discriminated between a target and other (probe, irrelevant) stimuli. One group of participants was tested in the easy task condition with low physical similarity among stimuli, the other group was tested in the difficult task condition with high physical similarity among stimuli. Using the base-to-peak P300 amplitude, the interaction effect of task difficulty and stimulus type was significant at $\alpha$=.1 level (p=.052). In the easy task condition the difference of P300 amplitude between the probe and the irrelevant stimuli was significant, while in the difficult task condition the difference was not significant. Using peak-to-peak P300 amplitude, on the other hand, the interaction effect of task difficulty and stimulus type was not significant with significant differences of P300 amplitude between the probe and the irrelevant stimuli in both task difficulty conditions. The difference of detection accuracy between task conditions was not significant with both measures of P300 amplitude although the difference was much smaller when peak-to-peak P300 amplitude was used. The results suggest that the efficiency of P300 CIT would not decrease even when the perceptual similarity among test stimuli is high.