P300-based Concealed Information Test Research Articles

Retroactive memory interference reduces false positive outcomes of informed innocents in the P300-based concealed information test

In the Concealed Information Test (CIT), differential responses between crime-relevant and crime-irrelevant items are indicative of concealed knowledge of a crime, and are used to classify an individual as either “guilty” or “innocent”. However, when crime-relevant items are leaked before the test, an innocent examinee can exhibit enhanced responses to the crime-relevant items, thus causing such examinee to be wrongly classified as guilty. In an attempt to solve this problem, we examined the role of retroactive memory interference (RI) in differentiating informed innocents from guilty participants, using a P300-based CIT. Participants acquired crime-related knowledge either by committing a mock crime (guilty group) or reading a paper that described a mock crime (informed innocent group). Subsequently, the participants within each condition were randomly assigned to either an RI group, where they were exposed to new crime-related details before the CIT, or a control group. We found an interaction between guilty and RI groups: in the guilty group, there was a significant difference in P300 amplitude between the probe and irrelevant items, regardless of RI manipulation, whereas in the informed innocent group, a difference in P300 amplitude between the probe and irrelevant items was significant only in the control group, but not in the RI group. This led to an improved detection rate of the informed innocents (31% for the control group vs. 77% for the RI group). These results suggest that RI manipulation could be used to reduce the false positive outcomes of informed innocents without affecting the detection rate of guilty participants.

An Independent Validation of the EEG-Based Complex Trial Protocol with Autobiographical Data and Corroboration of its Resistance to a Cognitively Charged Countermeasure.

The Complex Trial Protocol (CTP) is a P300-based Concealed Information Test (CIT). The theoretical underpinnings of the CIT in the context of law enforcement usage are sound. The CTP is said to effectively discriminate individuals who recognize novel and meaningful stimuli and to be countermeasure resistant. Forty-five undergraduate students were assigned to three groups and instructed to perform a computer task using autobiographical data in connection to a mock burglary script. P300 peak-to-peak amplitude differences between probe (surname) and irrelevant (patronymic foils) items accurately identified 100% (14/14) of Innocent Controls (IC), 94% (15/16) of Simply Guilty (SG) participants, and 93% (14/15) of Guilty Countermeasure (GCM) subjects who were asked to counter all stimuli by mentally counting backwards continuously during their test presentation. Increased number of mistakes during the test, from combined cognitive erroneous responses to pop quizzes and behavioral errors with button presses, significantly discriminated GCM from IC and SG individuals. GCM participants committed more errors than IC and SG which did not differ from one another. Reaction Time (RT) was only significant between GCM and IC groups. Implications for forensic issues are discussed.

The enhancing effect of incongruent verbal priming stimuli on the CIT effect with pictorial probes in the P300-based complex trial protocol

Previous research (Herring et al., 2011) indicated that certain types of incongruent verbal priming enhance responding to the subsequent (primed) stimuli. By priming participants in a P300-based Concealed Information Test (CIT), we examined the possible enhancement effects of priming stimuli in the P300 based Complex Trial Protocol (CTP) for face recognition. Participants were divided into two groups: one group with priming and one control group without. The probe (Pr) and irrelevants (Iall) of the two groups were faces, namely, pictures of the actor Tom Cruise (Pr) and of other unknown faces (Iall). One group had priming before Pr/Iall and one control group had no priming. The priming group was called the non-identical priming (NIP) group in which the verbal priming item (the name, “Bill Smith”) is identical with neither Pr nor any of the Ialls. The group without priming is the control group which is called the non-priming group (NP) that simply experiences the basic Complex Trial Protocol. Results were that non-identical priming produced larger CIT effects than the control group, which is consistent with earlier findings. Also, the amplitude of the probe of the NIP group is larger than that of the NP group, while their irrelevants didn't show any significant difference. This means that the incongruent verbal priming did enhance the P300 CIT effect for the probe, which could further improve the accuracy of CTP for the concealed information test.

The Accuracy of Permutation Test in P300-based Concealed Information Test

The Accuracy of Permutation Test in P300-based Concealed Information Test

The effect of retroactive memory interference on the P300-based Complex Trial Protocol (CTP)

In a P300-based concealed information test (CIT), an increased response to a crime-related “probe” item of interest suggests concealed knowledge. Because the CIT's detection ability is based on knowledgeable parties recognizing the key item, weakening the crime memory might decrease probe identifiability and reduce diagnostic power. Research on retroactive memory interference (RI) has shown that acquiring new information after encoding a memory can degrade the original memory, which suggests that RI might pose a threat to CITs. To test this, Gronau et al. (2015) had participants complete a mock-crime, followed by either a control task or a RI manipulation task, intended to impair the crime memory. Both the simple guilty control and RI groups were subdivided into three time delay conditions: 1/3 of participants immediately completed the task and CIT, another 1/3 completed the task and returned a week later for the CIT, and the remaining participants completed both the task and CIT a week later. Results showed that RI reduced memory of crime details and skin conductance responses, while respiration line length was unaffected. Here, we extend Gronau et al. (2015), using the Complex Trial Protocol (CTP) version of the P300-based CIT, to investigate the influence of RI on recognition. The CIT effect was obvious in all six group × time delay subconditions, as evidenced by their significantly larger probe vs. irrelevant amplitudes, high percentage of bootstrapped iterations where probe > irrelevants, bootstrapped mean amplitude differences, and satisfactory hit rates. However, these indices of the CIT effect did not differ based on group or time delay, as was the case for target response error rates and P300 latencies. The only outcome of interest to vary by group or time delay was behavioral response times: both probe and combined irrelevant responses were delayed in the control (simple guilty) group. Thus, the evidence suggests that the RI manipulation used here does not threaten the P300-based CTP's accuracy. Results are considered as they compare to previous work, and limitations and possible explanations for our results are discussed.

Effects of emotional arousal at memory encoding on the P300-based Concealed Information Test

Effects of emotional arousal at memory encoding on the P300-based Concealed Information Test

Item Roles Explored in a Modified P300-Based CTP Concealed Information Test

In this study, we introduced familiarity-related inducer items (expressions referring to the participant’s self-related, familiar details: “mine,” “familiar”; and expressions referring to other, unfamiliar details, e.g., “other,” “irrelevant”) to the Complex Trial Protocol version of the P300-based Concealed Information Test (CIT), at the same time using different item categories with various levels of personal importance to the participants (forenames, birthdays, favorite animals). The inclusion of inducers did not significantly improve the overall efficiency of the method as we would have expected considering that these inducers should increase awareness of the denial of the recognition of the probes (the true details of the participants), and hence the subjective saliency of the items (Lukács in J Appl Res Mem Cognit, 6:283–284, 2017a). This may be explained by the visual similarity of inducers to the probe and irrelevant items and the consequent distracting influence of inducers on probe-task performance. On the other hand, the CIT effect (probe-irrelevant P300 differences) was always lower for less personally important (low-salient) and higher for more personally important (high-salient) items.

Visual presentation modality's superiority in the detection of concealed information: A comparison of the efficiencies of the P300-based Complex Trial Protocol in visual versus auditory modalities

Some studies have shown a superiority of visual vs. auditory item presentation in the Complex Trial Protocol (CTP), which is a countermeasure-resistant version of the P300-based Concealed Information Test (CIT). But those studies used elaborately- rehearsed autobiographical information as stimuli, instead of incidentally-acquired crime-related information. Thus, the relative superiority of the visual as opposed to the auditory modality in detecting episodic crime-related information is still unknown. The present study also improved on the usual mock crime scenario by adding a mock disposal task between a mock theft and administration of a CTP test to increase stimulus saliency. In this CTP, the probe and the irrelevant items were presented visually or acoustically on alternating trials, while target and non-target stimuli were simultaneously presented in visual and auditory modalities. The results showed that the P300 amplitude differences of probe minus irrelevant items presented in the visual modality were significantly larger compared to the auditory modality, and the detection rate of the guilty participants was also significantly higher for the visual (14/16) versus auditory modality (5/16). These results suggest a superiority of visual vs. auditory presentation when a CTP is used to detect crime-related information in a mock crime scenario.

Detection of Concealed Information Using Multichannel Discriminative Dictionary and Spatial Filter Learning

P300-based concealed information test is a well-known approach for detection of deception. Previous studies only used the parietal channel, Pz, or at most three midline frontal, central, and parietal electrodes (Fz, Cz, and Pz); however, various observations indicate that the P300 component is distributed over a wide area on the scalp. In this paper, we propose a discriminative sparse representation model that effectively makes use of the multichannel concealed information test data. More specifically, a discriminative spatial filter is incorporated into the sparse model. Based on the proposed objective function, the elements of the model (dictionary, spatial filter and sparse code) are iteratively updated such that the discrimination power of the multichannel sparse model is improved. Furthermore, the effect of sparsity constraint on the spatial filter coefficients was investigated. In order to evaluate the performance of the multichannel model in distinguishing guilty subjects from innocent ones, 44 subjects went through a mock crime scenario, and subsequently their electroencephalography signals were recorded using eight electrodes. Experimental results show that the multichannel discriminative dictionary and spatial filter learning method was superior to other multichannel methods allowing classification of guilty and innocent participants with 95% accuracy. Moreover, the learned spatial filters are consistent with the physiological evidence regarding the distribution of P300 subcomponents over the scalp.

The false positive rate of P300-based concealed information test

The false positive rate of P300-based concealed information test

Emotional Arousal at Memory Encoding Enhanced P300 in the Concealed Information Test.

Previous studies have reported that the concealed information test (CIT) is a reliable and powerful method for detecting information. However, the external validity of the CIT studies has not been fully proven. In particular, few studies have examined the effects of emotional arousal at memory encoding on physiological responses in the CIT. The present study investigated the influence on the CIT of the magnitude of emotional arousal at memory encoding of a mock crime, using the P300 component of the event-related brain potential (ERP). In accord with the assumptions of excitation-transfer theory, we presented emotionally arousing pictures before a mock crime. Participants were randomly assigned to either a high emotional arousal group (n = 10) or a low emotional arousal group (n = 11), viewing pictures expected to arouse emotion at a high or low level, respectively. Subsequently, all participants enacted the same mock crime, in which they were instructed to stab a pillow with a sharp-edged tool (e.g., a kitchen knife or ice pick) as if harassing a mannequin lying on a bed. After the antecedent emotional experience, the P300-based CIT was conducted. Participants in the high arousal group showed significantly greater P300 amplitudes in response to a probe stimulus compared with the low arousal group. No differences were found between the groups in response to irrelevant stimuli. These results support the notion that emotional arousal influences the P300 in the CIT paradigm.

Inferior detection of information from collaborative versus individual crimes based on a P300 Concealed Information Test.

The present study used a P300-based Concealed Information Test (CIT) to detect individual and collaborative crimes and to explore whether or not the P300 index is effective in identifying collaborative crime members. Participants were divided into two groups to either steal a ring alone (individual group) or collaboratively with another companion participant (collaborative group) before taking the Complex Trial Protocol test that is regarded as an accurate version of the P300-based CIT. The ERP results revealed that both groups showed significantly larger P300s to probe (the ring) than to all irrelevant stimuli (other jewelery), but the P300 amplitude difference of probe stimulus versus irrelevant stimuli in the collaborative group was significantly less than that in the individual group. For the individual diagnosis, using P300 index, the detection rate was significantly inferior for collaborative crime than individual crime, probably related to weakness of collaborative encoding. The ROC curve comparisons showed the individual guilty was effectively discriminated from the simulated-innocent (AUC = .84) and from the collaborative guilty (AUC = .83), but the collaborative guilty was not discriminable from the simulated-innocent (AUC = .66). These findings suggest that collaborative encoding of crime-related information impacts the efficiency of the P300 index, and that the P300-based CIT is not applicable when used to identify collaborative crime perpetrators.

반응양식이 P300 숨긴정보검사의 정확도에 미치는 영향

반응양식이 P300 숨긴정보검사의 정확도에 미치는 영향

Attempts to Suppress Episodic Memories Fail but do Produce Demand: Evidence from the P300-Based Complex Trial Protocol and an Implicit Memory Test.

Instructions to voluntarily suppress memories of a mock crime have been reported to result in decreased P300 amplitude during a P300-based concealed information test (CIT) and reduced autobiographical Implicit Association Test (aIAT) D scores, supporting successful suppression. However, one such study, (Hu et al., Psychological science 26(7):1098-1106, 2015) used the P300-based Complex Trial Protocol with a 50-50 target to nontarget ratio, which could impose much response switching and thereby drain cognitive resources, also resulting in reduced P300. The present study replicated Hu et al. (Psychological science 26(7):1098-1106, 2015) with one major variation-a less intrusive 20-80 target to nontarget ratio that required less response switching. Detection rates were high using both the brainwave-based CIT (90% accuracy) and the aIAT (87% accuracy). However we found no significant differences between the suppression and simple guilty groups on the major indices of concealed information detection, which compare probe and irrelevant P300 responses. While we did find that overall P300 amplitude was reduced in the suppression group, this reduction was not specific to probe responses. Additionally, while there were group differences in aIAT hit rates, there were no differences in aIAT D scores. Taken together, these findings suggest that the previously demonstrated reductions in P300 are a reflection of task demand rather than of effective voluntary memory suppression.

P300 amplitude at Pz and N200/N300 latency at F3 differ between participants simulating suspect versus witness roles in a mock crime.

Based on the autonomic nervous system (ANS) study by klein Selle, Verschuere, Kindt, Meijer, & Ben Shakhar (2016), 15 participants pretended to perform a crime shown on a video, which 16 other participants pretended to witness. Both groups then experienced a P300-based Concealed Information Test (CIT) protocol called the complex trial protocol. Both groups showed CIT effects, with a larger probe than irrelevant P300s at Pz. However, this effect was significantly larger in the suspect group. In contrast, only the suspect group showed delayed N200/N300 responses at F3-putative inhibitory signs. This supports the klein Selle et al. (2016) ANS study in that the suspect versus witness role-playing manipulation differentially affected inhibitory (vs. orienting) aspects of the CIT situation. Our results are also consistent with Ambach, Stark, Peper, & Vaitl (2008), who saw the same autonomic response fractionation as klein Selle et al., but using Furedy's differentiation of deception method (Furedy, Davis, & Gurevich, 1988). These similarities are discussed.

High Emotional Arousal Enables Subliminal Detection of Concealed Information

The Concealed Information Test (CIT) is an information-detecting technique for criminal investigations. Although it has been shown that emotional arousal plays a specific role in the CIT, the mechanisms by which emotional arousal affects the CIT are unclear. The main purpose of this study was to elucidate the processing pathway for stimuli encoded with emotional arousal in a mock crime before the CIT. In this study, participants viewed emotionally arousing pictures before the mock crime. Participants were assigned randomly to either a high or low emotional arousal group, viewing pictures expected to arouse emotion at a high or low level, respectively. Subsequently, all participants enacted the same mock crime, in which they were instructed to stab a pillow with a sharp-edged tool (e.g., kitchen knife or ice pick) as if to harass a woman lying on a bed. After the antecedent emotional experience, a P300-based CIT was conducted using subliminal and supraliminal presentation methods. The results revealed a significantly greater CIT effect on the P300 event-related potential (ERP) component in the High Arousal group compared with the Low Arousal group, under both subliminal and supraliminal conditions. The detection of concealed information was successful only in the High Arousal group under subliminal conditions, whereas detection was successful regardless of the emotional arousal group under supraliminal conditions. These results provide strong evidence that emotional arousal can increase P300 amplitude during responses to concealed information in the CIT. This suggests that concealed information may be automatically processed via the bottom-up route in the CIT, but only when it is encoded with high emotional arousal.

The first independent study on the complex trial protocol version of the P300-based concealed information test: Corroboration of previous findings and highlights on vulnerabilities

More than a dozen studies of the Complex Trial Protocol (CTP) version of the P300-based Concealed Information Test have been published since its introduction (Rosenfeld et al., 2008), and it has been fairly consistently proven to provide high accuracy and strong resistance to countermeasures (Rosenfeld et al., 2013). However, no independent authors have verified these findings until now. In the present, first independent study, we corroborate the accuracy and countermeasure-resistance of the CTP, when the probe item (critical presented information, e.g., crime detail; P) vs. all irrelevant items (Iall) comparison is used for classifying participants as guilty or innocent, but we also show that the CTP is severely vulnerable to countermeasures, when the P vs. the irrelevant item with the largest P300 responses (Imax) comparison is used. This latter measure can be defeated by creating “oddball” items among the irrelevant items (through targeting them with covert responses), and thereby making their P300 responses statistically indistinguishable from those of the probe item. Practical implications are discussed.

Superiority of visual (verbal) vs. auditory test presentation modality in a P300-based CIT: The Complex Trial Protocol for concealed autobiographical memory detection

This paper continues our efforts to determine which modality is best for presentation of stimuli in the P300-based concealed information test (CIT) called the Complex Trial Protocol (CTP). The first part of the CTP trial involves presentation of the key probe or irrelevant stimuli, and is followed by presentation of target (T) or non-target (NT). In Rosenfeld et al. (2015), probes and irrelevants regularly alternated modality over trials, but Ts and NTs were always visual. In the present study, (in both its experiments, EXP 1 and EXP 2), probes and irrelevants alternated modalities on successive trials, as before. In present EXP 1, Ts and NTs were always auditory, but in EXP 2, they were simultaneously auditory and visual. Probe P300 data were different in each study: In Rosenfeld et al. (2015) and EXP 2 here, the bootstrap-based detection rates based on probe-minus-irrelevant differences, significantly differed favoring visual probe and irrelevant presentation modality. In EXP 1 here, detection rates were the same for the two modalities. In Rosenfeld et al. (2015) there was no main effect of probe modality, visual vs. auditory on probe-minus-irrelevant P300 difference. There were such effects here in EXP 1 (p<0.08, effect size=0.19) and EXP 2 (p<0.02, effect size=0.31), favoring the visual modality. Probe P300 latencies were shorter for visual than for auditory stimuli in Rosenfeld et al. (2015), a trend specifically reversed in the present pair of studies. RT was faster for visual stimuli in the present studies. The T and NT modality appears to interact with probe/irrelevant modality, and the best protocol for detecting concealed information is with the 2015 study protocol or that of EXP 2, using visual stimulus presentation.

An examination of same ratio task using simultaneous auditory and visual stimuli presentation of a P300-based concealed information test

An examination of same ratio task using simultaneous auditory and visual stimuli presentation of a P300-based concealed information test

Effects of Countermeasures on P300-based Concealed Information Test with Short Inter-Stimulus Interval

본 연구에서는 관련자극이 한 개이고 자극간 제시간격이 1초인 P300 숨긴정보검사(P300 CIT)가 부분 매칭 대응수단에 영향을 받는지 검증하였으며, 대응수단의 사용을 탐지할 수 있는 방법을 탐색하였다. 네 개의 무관련자극 중 하나의 무관련자극에 특정 반응을 하는 조건(1CM 조건)과 두 개의 무관련자극에 특정 반응을 하는 조건(2CM 조건)에서 대응수단의 효과를 검증하였다. 각 조건에서 손가락 또는 발가락을 움직이는 물리적 대응수단과 마음속으로 어머니 또는 아버지의 이름을 부르는 정신적 대응수단을 사용하였다. 실험결과, 물리적 대응수단과 정신적 대응수단은 모두 P300 CIT의 결과에 큰 영향을 미치는 것으로 나타났다. 대응수단을 사용하지 않은 경우에 P300 CIT의 정확탐지율은 71%였던 반면, 물리적 대응수단을 사용한 경우에는 1CM 조건과 2CM 조건의 정확탐지율은 각각 0%와 14%였으며, 정신적 대응수단을 사용한 경우에는 1CM 조건과 2CM 조건의 정확탐지율이 모두 14%였다. ERP들 간의 상관계수로 대응수단의 탐지가능성을 평가하였다. 거짓을 말하였으나 거짓을 말하지 않은 것으로 잘못 판단된 사례들을 대상으로, 무관련자극의 ERP와 관련자극의 ERP 간 상관계수가 무관련자극의 ERP와 목표자극의 ERP 간 상관계수보다 더 큰지 확인하였다. 물리적 대응수단집단의 100%와 정신적 대응수단집단의 92%가 이러한 경우에 해당한 반면에 단순유죄집단은 33%만 이러한 양상을 보였다. ERP간 상관계수를 이용한 대응수단 사용의 탐지가능성을 논의하였다.