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.     

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.     

The impact of prior knowledge from participant instructions in a mock crime P300 Concealed Information Test

In P300-Concealed Information Tests used with mock crime scenarios, the amount of detail revealed to a participant prior to the commission of the mock crime can have a serious impact on a study's validity. We predicted that exposure to crime details through instructions would bias detection rates toward enhanced sensitivity. In a 2 × 2 factorial design, participants were either informed (through mock crime instructions) or naïve as to the identity of a to-be-stolen item, and then either committed (guilty) or did not commit (innocent) the crime. Results showed that prior knowledge of the stolen item was sufficient to cause 69% of innocent–informed participants to be incorrectly classified as guilty. Further, we found a trend toward enhanced detection rate for guilty–informed participants over guilty–naïve participants. Results suggest that revealing details to participants through instructions biases detection rates in the P300-CIT toward enhanced sensitivity.     

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.     

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.     

Memory detection with the Concealed Information Test: A meta analysis of skin conductance,respiration, heart rate,and P300 data

The Concealed Information Test (CIT) uses psychophysiological measures to determine the presence or absence of crime‐related information in a suspect's memory. We conducted a meta‐analysis on the validity of the CIT based on four physiological measures—skin conductance response (SCR), respiration line length (RLL), changes in heart rate (HR), and enhanced amplitudes of the P300 component of the event‐related potential (P300). This meta‐analysis relied on laboratory studies that used either the mock‐crime or the personal‐item paradigm. Results showed a mean effect size (d*) of 1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300. However, P300 outperformed SCR only in the personal‐item paradigm, but not in the mock‐crime paradigm. Motivation level, number of questions, publication year, and the inclusion of innocent participants emerged as significant moderators for the SCR, while only the type of paradigm used moderated the P300 effect.     

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.     

Financial incentive does not affect P300 (in response to certain episodic and semantic probe stimuli) in the Complex Trial Protocol (CTP) version of the Concealed Information Test (CIT) in detection of malingering

Previous research indicated that the skin conductance response of the autonomic nervous system in the Concealed Information Test (CIT) is typically increased in subjects who are financially and otherwise incentivized to defeat the CIT (the paradoxical “motivational impairment” effect). This is not the case for RT‐based CITs, nor P300 tests based on the three‐stimulus protocol for detection of cognitive malingering (although these are not the same as CITs). The present report is the first attempt to study the effect of financial motivation on the P300‐based Complex Trial Protocol using both episodic and semantic memory probe and irrelevant stimuli. The Test of Memory Malingering (TOMM) was used to validate behavioral differences between the two groups we created by offering one (paid) group but not another (unpaid) group a financial reward for beating our tests. Group behavioral differences on the TOMM did confirm group manipulations. Probe‐minus‐irrelevant P300 differences did not differ between groups, although as previously, semantic memory‐evoked P300s were larger than episodic memory‐evoked P300s.     

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.     

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.     

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.     

Single versus multiple probe blocks of P300-based concealed information tests for self-referring versus incidentally obtained information

The aim of the present study was to compare two protocols and two information types on detection of concealed knowledge. Four independent groups of subjects were run. Two were tested on probe stimuli of a self-referring (AUTO) nature and two were tested on incidentally acquired details of a mock crime (MOCK). Each pair of groups was run either in a one-probe (1PB) or multiple probe (6PB) block. In the single probe block, which was repeated three times with a different probe on each block, one probe item was randomly repeated multiple times in a Bernoulli series with frequently presented, meaningless or irrelevant items. There was also a rare target item designed to force attention to the stimulus screen. All stimulus types were of the same category within each block. In contrast, in the multiple probe (and category) block, rare probes, rare targets and frequent irrelevant items were repeatedly presented in a Bernoulli series within one block. Major results: There was a difference in task demand as measured by reaction time between the two protocols (the multiple probe protocol was more demanding), and a difference trend in P300 detection sensitivity between protocols for both information types combined in favor of the 1PB (p<.07). With both protocols combined, there was a trend (p<.07) favoring detection of familiar versus incidentally learned information. In terms of P300 amplitudes, both protocols showed the usual result that P300 to probes was greater than that to irrelevants. Also, as with detection rates, self-referring information was better detected in terms of Probe-Irrelevant P300 amplitude differences than mock crime information, regardless of protocol. There was no effect of time passage across the repeated blocks of the one-probe protocol. Methodological problems with the multiple probe protocol as utilized in most recent publications are discussed.     

Review of recent studies and issues regarding the P300-based complex trial protocol for detection of concealed information

In this review, the evolution of new P300-based protocols for detection of concealed information is summarized. The P300-based complex trial protocol (CTP) is described as one such countermeasure (CM)-resistant protocol. Recent lapses in diagnostic accuracy (from 90% to 75%) with CTPs applied to mock crime protocols are summarized, as well as recent enhancements to the CTP which have restored accuracy. These enhancements include 1) use of performance feedback during testing, 2) use of other ERP components such as N200 in diagnosis, 3) use of auxiliary tests, including the autobiographical implicit association test, as leading to restored diagnostic accuracy, and 4) a study of the mechanisms underlying CMs. A novel, doubly efficient version of the CTP involving presentation of two probes in one trial is described as a new way to improve accuracy to levels above 90% in mock crime situations. Finally, a thorough analysis of the legal issues surrounding use of the CTP in U.S. is given.     

Countermeasure mechanisms in a P300-based concealed information test

We recently introduced an accurate and countermeasure (CM)-resistant P300-based deception detection test ( J.P. Rosenfeld et al., 2008 ). When subjects use CMs to all irrelevant items in the test, the probe P300 is increased rather than reduced, as in previous P300-based deception protocols, allowing detection of CM users. Evidence herein suggests this is partly due to an omit effect; the probe was the only uncountered item. Three groups were tested: a guilty omit probe group performed an explicit response to each irrelevant item but not to the probe, an innocent omit irrelevant group saw only irrelevant items and omitted a response to one item, and a guilty no omit group had a concealed information item as probe and performed an explicit response to each. We found a greater P300 amplitude to probes in the guilty omit probe condition as compared with the other two conditions, indicating a P300 enhancing effect of omitting a response to a single stimulus.     

Necessity of the target discrimination in the P300-based complex trial protocol test for concealed information

The two most common types of ERP-based protocols to detect concealed information are the 3-stimulus protocol (3SP) and Complex Trial Protocol (CTP). Both protocols traditionally include presentation of a target (a stimulus with assigned significance requiring a unique behavioral response). The intention of the target presentation is forcing subjects to pay attention to all stimuli, especially to guilty knowledge stimuli, called probes. It was unclear though, how the presence of a targets influences probe recognition, and thus, the concealed information test (CIT) effect—the difference in P300 response to the probe and Irrelevant (crime-unrelated) stimuli. The question of target necessity was first raised in relation to the 3SP, and it was found that although omitting target stimuli reduced P300 amplitudes for all probe and irrelevant stimuli, the CIT effect was not reduced. The current study investigated how the presence or absence of the target/nontarget discrimination in the CTP affects the CIT effect, by comparing two CTP groups both with (T) and without (NT) the target/nontarget discrimination. The results demonstrated that this discrimination significantly increases the P300 effect. We found a greater P300 CIT effect in the T group than in the NT group, suggesting that for field use, it is better to retain the target discrimination in the CTP. CIT effects were also seen with P300 latency, but not reaction time.     

Psychopathy and Detection of Deception In a Prison Population

The effectiveness of detection of deception was evaluated with a sample of 48 prisoners, half of whom were diagnosed psychopaths. Half of each group were “guilty” of taking $20 in a mock crime and half were “innocent.” An examiner who had no knowledge of the guilt or innocence of each subject conducted a field-type interview followed by a control question polygraph examination. Electrodermal, respiration, and cardiovascular activity was recorded, and field (semi-objective) and quantitative evaluations of the physiological responses were made. Field evaluations by the examiner produced 88% correct, 4% wrong, and 8% inconclusives. Excluding inconclusives, there were 96% correct decisions. Using blind quantitative scoring and field evaluations, significant discrimination between “guilty” and “innocent” subjects was obtained for a variety of electrodermal, respiration, and cardiovascular measures. Psychopaths were as easily detected as nonpsychopaths, and psychopaths showed evidence of stronger electrodermal responses and heart rate decelerations. The effectiveness of control question techniques in differentiating truth and deception was demonstrated in psychopathic and nonpsychopathic criminals in a mock crime situation, and the generalizability of the results to the field situation is discussed.     

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.     

The role of comparison questions in physiological detection of deception

Comparison questions in physiological detection of deception were studied with 60 “guilty’ and 60 “innocent’ participants in a mock crime experiment. Different types of comparison questions were used in four conditions: relevant–irrelevant (R-I) participants answered only relevant and neutral questions; trivial directed lie participants were instructed to lie to three of the six neutral questions; personal directed lie participants were instructed to lie to personally relevant questions; and probable lie participants received traditional probable lie comparison questions. Respiration, cardiovascular, vasomotor, and electrodermal activity were recorded. Manipulation of the comparison questions produced different patterns of physiological responses for innocent but not for guilty participants. The R-I test produced an unacceptable rate of false positive decisions.     

Detecting Concealed Information Using Functional Near-Infrared Spectroscopy

The present study focused on the potential application of fNIRS in the detection of concealed information. Participants either committed a mock crime or not and then were presented with a randomized series of probes (crime-related information) and irrelevants (crime-irrelevant information) in a standard concealed information test (CIT). Participants in the guilty group were instructed to conceal crime-related information they obtained from the mock crime, thus making deceptive response to the probes. Meanwhile, their brain activity to probes and irrelevants was recorded by functional near-infrared spectroscopy (fNIRS). At the group level, we found that probe items were associated with longer reaction times and greater activity in bilateral dorsolateral prefrontal cortex and supplementary motor cortex than irrelevant items in the guilty group, but not in the innocent group. These findings provided evidence on neural correlates of recognition during a CIT. Finally, on the basis of the activity in bilateral dorsolateral prefrontal cortex and supplementary motor cortex, the correct classification of guilty versus innocent participants was approximately 75 % and the combination of fNIRS and reaction time measures yielded a better classification rate of 83.3 %. These findings illustrate the feasibility and promise of using fNIRS to detect concealed information.     

An Evaluation of Field Techniques in Detection of Deception

Field techniques of detecting deception were evaluated using a mock crime situation. Thirty-six Ss were “guilty” of taking $10, and 36 Ss were “innocent,” A field-type interview was followed by a zone comparison control-question polygraph examination. A Keeler field polygraph was used to record physiology activity, and field (semi-objective) and quantitative evaluations of the charts were made. Those who evaluated the charts were not informed about the “guilt” or “innocence” of each S. Using field evaluations, there were 53% correct. 12% incorrect, and 35% inconclusives. Excluding inconclusives there were 81% correct decision. using quantitative scoring, significant discriination between “guilty” and “innocent” was obtaindd with skin resistance, cardiovascular, and respiration measures, with skin resistance best. Field evaluations also produced significant discrimination for all three measures. Blind evaluations of the charts by 5 additional examiners produced high agreement among examiner decisions and a mean correlation of .86 among total scores. Thus, the effectiveness of commonly used field techniques and equipment in differentiating truth and deception was demonstrated in a laboratory setting.