N200 and P300 as orthogonal and integrable indicators of distinct awareness and recognition processes in memory detection

In an event‐related potential (ERP)‐based concealed information test (CIT), we investigated the effect of manipulated awareness of concealed information on the ERPs. Participants either committed a mock crime or not (guilty vs. innocent) before the CIT, and received feedback regarding either specific (high awareness) or general (low awareness) task performance during the CIT. We found that awareness and recognition of the crime‐relevant information differentially influenced the frontal‐central N200 and parietal P300: Probe elicited a larger N200 than irrelevant only when guilty participants were in the high awareness condition, whereas the P300 was mainly responsive to information recognition. No N200‐P300 correlation was found, allowing for a combined measure of both yielding the highest detection efficiency in the high awareness group (AUC = .91). Finally, a color‐naming Stroop task following the CIT revealed that guilty participants showed larger interference effects than innocent participants, suggesting that the former expended more attentional resources during the CIT.     

Emotional arousal modulates the encoding of crime-related details and corresponding physiological responses in the Concealed Information Test

Previous studies demonstrated that concealed crime-related memories can be validly identified using the Concealed Information Test (CIT). However, its field applicability is still debated, and it is specifically unknown how emotional arousal during a crime would influence CIT results. In the current study, emotional arousal during a mock crime and the time delay between mock crime and CIT examination were manipulated. At the immediate and the delayed CIT occasion, central crime details were better remembered than peripheral ones and enhanced emotional arousal further reduced memory for peripheral information. Electrodermal, respiratory, and cardiovascular responses to central crime details were strong and CIT validity was unaffected by delaying the test when arousal was induced during the mock crime. These findings indicate that emotional arousal might facilitate the detection of concealed information some time after a crime occurred.     

A mock terrorism application of the P300‐based concealed information test

Previous studies examining the P300‐based concealed information test typically tested for mock crime or autobiographical details, but no studies have used this test in a counterterrorism scenario. Subjects in the present study covertly planned a mock terrorist attack on a major city. They were then given three separate blocks of concealed information testing, examining for knowledge of the location, method, and date of the planned terrorist attack, using the Complex Trial Protocol ( Rosenfeld et al., 2008 ). With prior knowledge of the probe items, we detected 12/12 guilty subjects as having knowledge of the planned terrorist attack with no false positives among 12 innocent subjects. Additionally, we were able to identify 10/12 subjects and among them 20/30 crime‐related details with no false positives using restricted a priori knowledge of the crime details, suggesting that the protocol could potentially identify future terrorist activity.     

Combining skin conductance and forced choice in the detection of concealed information

An advantage of the concealed information polygraph test (CIT) is that its false positive rate is determined on statistical grounds, and can be set a priori at arbitrary low levels (i.e., few innocents declared guilty). This criterion, however, inevitably leads to a loss of sensitivity (i.e., more guilty suspects declared innocent). We explored whether the sensitivity of a CIT procedure could be increased by adding an independent measure that is based on an entirely different psychological mechanism. In two experiments, we explored whether the accuracy of a CIT procedure could be increased by adding Symptom Validity Testing (SVT), a relatively simple, forced-choice, self-report procedure that has previously been used to detect malingering in various contexts. Results of a feigned amnesia experiment but not from a mock crime experiment showed that a combination measure of both tests yielded better detection than either test alone.     

Mock crime application of the Complex Trial Protocol (CTP) P300‐based concealed information test

The Complex Trial Protocol (CTP), was shown to be an improvement over the previous “three stimulus” P300‐based concealed information tests (CITs). Not only was it highly accurate with autobiographical information but was also resistant to the use of countermeasures (CMs). The current study applied the CTP to the detection of incidentally acquired information in a mock crime scenario. In previous “three stimulus” mock crime studies utilizing P300‐based CITs, participants memorized a guilty knowledge item(s). Special care was taken in the current study to ensure that participants' knowledge of the guilty item in the mock crime was obtained only during the commission of the act in order to bolster ecological validity. Overall, 92% of all participants in guilty, innocent, and countermeasure conditions were correctly classified. CM use was again indexed by reaction times (RTs).     

Using pretest data to screen low‐reactivity individuals in the autonomic‐based concealed information test

The concealed information test (CIT) can be used to assess whether an individual possesses crime‐related information. However, its discrimination performance has room for improvement. We examined whether screening out participants who do not respond distinctively on a pretest improves the diagnosticity of a mock‐crime CIT. Before conducting the CIT, we gave a pretest to 152 participants, 80 of whom were assigned as guilty. Pretest screening significantly improved the diagnostic value of the mock‐crime CIT; however, it also led to a substantial number of undiagnosed participants (33.6%). Pretest screening holds promise, but its application would benefit from dedicated measures for screening out participants.     

Innocence, Information, and the Guilty Knowledge Test in the Detection of Deception

The purpose of this detection of deception experiment was to study the assumption of the Guilty Knowledge Test that subjects with guilty knowledge will be classed as guilty by the test regardless of their actual guilt or innocence. Prior to a polygraph examination, three groups of innocent subjects were given the same crime-relevant information as members of a group guilty of a mock crime. These innocent subjects either witnessed the crime, were told the crime details, or carried out innocent activities involving crime-relevant information. An additional group of innocent subjects had no crime-relevant information. Analysis of the Guilty Knowledge Test results showed that the detection scores of guilty subjects were higher than those in any of the innocent groups. In fact, with the exception of the innocent activities group, the innocent informed subjects did not differ from those in the uninformed group. The major conclusion is that subjects may have crime-relevant information and not be classed, based on the detection scores, as guilty.     

Within-individual discrimination on the Concealed Information Test using dynamic mixture modeling

Whether an examinee has information about a crime is determined by the Concealed Information Test based on autonomic differences between the crime-related item and other control items. Multivariate quantitative statistical methods have been proposed for this determination. However, these require specific databases of responses, which are problematic for field application. Alternative methods, using only an individual's data, are preferable, but traditionally such within-individual approaches have limitations because of small data sample size. The present study proposes a new within-individual judgment method, the hidden Markov discrimination method, in which time series-data are modeled with dynamic mixture distributions. This method was applied to experimental data and showed sufficient potential in discriminating guilty from innocent examinees in a mock theft experiment compared with performance of previous methods.     

Psychophysiological and behavioral measures for detecting concealed information: the role of memory for crime details

This study examined the role of memory for crime details in detecting concealed information using the electrodermal measure, Symptom Validity Test, and Number Guessing Test. Participants were randomly assigned to three groups: guilty, who committed a mock theft; informed-innocents, who were exposed to crime-relevant items; and uninformed-innocents, who had no crime-relevant information. Participants were tested immediately or 1 week later. Results showed (a) all tests detected the guilty in the immediate condition, and combining the tests improved detection efficiency; (b) tests' efficiency declined in the delayed condition, mainly for peripheral details; (c) no distinction between guilty and informed innocents was possible in the immediate, yet some distinction emerged in the delayed condition. These findings suggest that, while time delay may somewhat reduce the ability to detect the guilty, it also diminishes the danger of accusing informed-innocents.     

Combining the P300-complex trial-based concealed information test and the reaction time-based autobiographical implicit association test in concealed memory detection

Despite the P300-concealed information test's validity in detecting concealed memory when it is conducted immediately after the mock crime, whether the P300-CIT's detection efficiency is moderated by time delay remains unknown. Here, we conducted a mock crime study in which guilty participants were tested immediately after the mock crime or 1 month later. An innocent group was also tested. Assuming that the autobiographical Implicit Association Test (aIAT) and the P300-CIT rely on nonoverlapping mechanisms for memory detection, participants were tested using both the P300-CIT and the reaction time (RT)-based aIAT. Results suggested that the sensitivity of both tests remains even after the 1-month delay. The indicators from the RT-aIAT and P300-CIT were uncorrelated, thus combining P300-CIT and aIAT data further increased the efficiency of memory detection.     

Identifying concealment‐related responses in the concealed information test

The concealed information test (CIT) assesses an examinee's recognition of a crime‐relevant item using physiological measures. However, a guilty examinee not only recognizes the crime‐relevant item but also conceals the recognition intentionally. In this study, we attempted to identify the effect of concealing the recognition on event‐related potentials and autonomic responses. After committing a mock theft of two items, 30 participants received two CITs: one for an item that they had to conceal, and the other for an item that they had disclosed. N2, P3, heart rate, skin conductance, and cutaneous blood flow differed between crime‐relevant and irrelevant items in both CITs. In contrast, late positive potential and respiration differed between crime‐relevant and irrelevant items only when the examinee needed to conceal. The former measures appear to be related to orienting process, whereas the latter to controlled process related to concealment.     

Detection of deception about multiple, concealed, mock crime items, based on a spatial-temporal analysis of ERP amplitude and scalp distribution

Three groups, two-probe (2PG), three-probe (3PG), and control (CG), performed a mock crime. 2PG and 3PG stole two and three items, respectively, after a baseline "truth block"; the CG stole nothing. Subjects all completed a second "lie block" after the mock crime. There were four stimuli in truth and lie blocks: truth probe (TP), truth irrelevant (TI), lie probe (LP), and lie irrelevant (LI). Stolen items were probes; other items were irrelevants. Spatial-temporal PCA was applied. For the 2PG, subjects' frontal-central component amplitudes in the 520–644-ms temporal component were significantly more positive for LP than for LI stimulus. Individually, 12 of 14 subjects (far better detection than results [72% hits] with non-PCA analyses methods) in the 2PG were detected, with a false positive rate of 4 of 14 in the CG. No difference between LP and LI was found in 3PG data. In summary, spatial-temporal PCA improves detection of concealed information.     

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.     

Influence of countermeasures on the validity of the Concealed Information Test

The Concealed Information Test (CIT) is a psychophysiological technique that allows for detecting crime‐related knowledge. Usually, autonomic response measures are used for this purpose, but ocular measures have also been proposed recently. Prior studies reported heterogeneous results for the usage of countermeasures (CM) to corrupt the CIT's validity, depending on the CM technique and the dependent measure. The current study systematically compared the application of physical and mental CM on autonomic and ocular measures during the CIT. Sixty participants committed a mock crime and were assigned to one of three guilty conditions: standard guilty (without CM), physical CM, or mental CM. An additional group of 20 innocents was investigated with the same CIT to calculate validity estimates. Electrodermal responses were more vulnerable for CM usage compared to heart rate and respiration, and physical CM were more effective than mental CM. Independent of CM usage, a combined score of autonomic responses enabled a valid differentiation between guilty and innocent examinees. Fixations and blinks also allowed for detecting crime‐related knowledge, but these measures were more affected by CM application than autonomic responses. The current study delivered further evidence that CM differentially impact physiological and ocular responses in the CIT. Whereas individual data channels were strongly affected by CM usage, a combination of different response measures yielded a relatively stable differentiation of guilty and innocent examinees when mental CM were used. These findings are especially relevant for field applications and might inspire future studies to detect or prevent CM usage in CIT examinations.     

Salience of Guilty Knowledge Test items affects accuracy in realistic mock crimes.

Guilty Knowledge Test measuring electrodermal reactions was carried out in order to investigate the quality of different questions and the validity of the test in a situation that resembled a true crime. Fifty participants were randomly assigned to commit one of two realistic mock crimes, and were later tested with GKTs concerning both the crime they had enacted and the one they had no knowledge of. Different scoring systems (SCRs and peak amplitudes as well as raw and standardised scores) were employed and compared when analyzing the results. Although there were some false positives, the test was able to differentiate between the groups of guilty and innocent participants. With the best scoring systems, the test was able to classify up to 84% of the innocent and up to 76% of the guilty correctly according to a logistic regression analysis. ROC areas reflecting these same results reached values above .80. Questions on matters that demanded the participants' attention and were easier to remember had better discriminative power. With nearly all scoring methods, there was a significant interaction between the salience of the relevant items and the guilt of the participants. Participants reacted more strongly to salient relevant items when they were guilty, while no different reactions were observed for the non-salient items between guilty and innocent participants. It is suggested that, although the Guilty Knowledge Test appears to be a valid measure of guilty knowledge even in crimes that are close to real crimes, the principles on which guilty knowledge test questions are constructed should be more clearly specified.     

A novel Dual Probe Complex Trial Protocol for detection of concealed information

In simply guilty (SG), countermeasure‐using guilty (CM), and innocent (IN) subjects, a new concealed information test, the P300‐based Dual Probe Complex Trial Protocol was tested in a mock crime scenario. It combines an oddball protocol with two stimuli (probe, irrelevant) and another with three stimuli (probe, irrelevant, target) into one trial, doubling detected mock crime information per unit time, compared to previous protocols. Probe‐irrelevant amplitude differences were significant in SG and CM, but not IN subjects. On a measure from both two and three stimulus protocol parts of the Dual Probe Complex Trial Protocol trial, accuracy was 94.7% (based on a .9 bootstrap criterion). The criterion‐independent area (AUC) under the receiver operating characteristic (from signal detection theory) measuring SG and CM versus IN discriminability averaged .92 (in a range of 0.5–1.0). Countermeasures enhanced irrelevant (not probe) P300s in CM groups.     

Increasing the number of irrelevant stimuli increases ability to detect countermeasures to the P300-based Complex Trial Protocol for concealed information detection

We previously found that simultaneously executing a mental countermeasure and an explicit required response impairs reaction time (RT)-based detection of countermeasure use in a P300- based concealed information test. To address this issue, we increased the numbers of irrelevant stimuli to eight, and manipulated the proportions of to-be-countered irrelevant stimuli from 25% to 50% to 75% in three groups. RESULTS: Based on P300 data, 100% of the simple guilty (no countermeasure use) and 92% of the innocent subjects were correctly identified as having or not having concealed information. In the countermeasure groups, detection rates varied from 71% to 92% across the different groups. Notably, in the present study with eight irrelevant items, simultaneous countermeasure use was indicated by elevated RT in the 50% and 75% countermeasure proportion groups, which it was not, previously, with 50% (two) countermeasures and four irrelevants.     

Facial Skin Surface Temperature Changes During a “Concealed Information” Test

When individuals who commit a crime are questioned, they often show involuntary physiological responses to remembered details of that crime. This phenomenon is the basis for the concealed information test, in which rarely occurring crime-related details are embedded in a series of more frequently occurring crime-irrelevant items while respiratory, cardiovascular, and electrodermal responses are recorded. Two experiments were completed to investigate the feasibility of using facial skin surface temperature (SST) measures recorded using high definition thermographic images as the physiological measure during a concealed information test. Participants were randomly assigned to nondeceptive or deceptive groups. Deceptive participants completed a mock-crime paradigm. A focal plane array thermal imaging radiometer was used to monitor SST while crime-relevant and crime-irrelevant items were verbally presented to each participant. During both experiments, there were significant facial SST differences between deceptive and nondeceptive participants early in the analysis interval. In the second experiment, hemifacial (i.e., “half-face” divided along the longitudinal axis) effects were combined with the bilateral responses to correctly classify 91.7% of participants. These results suggest that thermal image analysis can be effective in discriminating deceptive and nondeceptive individuals during a concealed information test.     

Event-related potentials increase the discrimination performance of the autonomic-based concealed information test

The concealed information test (CIT) assesses an examinee's crime-relevant memory on the basis of physiological differences between crime-relevant and irrelevant items. The CIT based on autonomic measures has been used for criminal investigations, while the CIT based on event-related potentials (ERPs) has been suggested as a useful alternative. To combine these two methods, we developed a quantification method of ERPs measured in the autonomic-based CIT where each item was repeated only 5 times. Results showed that the peak amplitude of the ERP difference wave between crime-relevant and irrelevant items could discriminate between guilty and innocent participants effectively even when only 5 trials were used for averaging. This ERP measure could detect some participants who were missed by the autonomic measures. Combining the ERP and autonomic measures significantly improved the discrimination performance of the autonomic-based CIT.     

Deleterious effects of probe‐related versus irrelevant targets on the “CIT effect” in the P300‐ and RT‐based three‐stimulus protocol for detection of concealed information

Two groups of participants committed the same mock crime in which one of two items, a watch or a ring, was removed from a drawer and concealed. One group, the crime‐familiar group next experienced a three‐stimulus protocol (3SP), a Concealed Information Test (CIT), in which they were tested on the stolen (probe) item presented in a random series of five irrelevant (unseen) stimuli from the same jewelry category. A left‐hand button press, meaning “I don't recognize” was to follow each of these six items. A right‐hand press (“I do recognize”) was to follow the one other presented item, the target item, which in the case of the crime‐familiar group was the other, not‐stolen item in the drawer at the mock crime scene. For the other crime‐unfamiliar group, the target was a sixth unseen irrelevant item as in the original P300 CIT. In terms of P300 latency and reaction time (RT), crime‐familiar participants processed all stimuli faster than crime‐unfamiliar participants. The CIT effects (probe‐minus‐irrelevant differences) for crime‐familiar group members were inferior to those of crime‐unfamiliar group members for RT and P300 amplitude measures. Thus, familiar targets negatively impact the 3SP.