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

Area measure of skin conductance in the Concealed Information Test

Skin conductance (SC) is one of the indices commonly used in the autonomic Concealed Information Test (CIT), but SC amplitude is sometimes difficult to quantify. This study investigated the applicability of SC area to the CIT as an unambiguous measure of SC. Secondary analyses of an existing dataset indicated that SC area could be used to classify examinees according to their knowledge status, although the equivalence of its performance with the SC amplitude was inconclusive. Classification performance was best when the SC signal was converted to the difference from question onset and summed over 10 s after question onset. SC area produced relatively consistent evaluations of differential responses based on the amplitude for inter-item comparisons. In addition, the classification performance of SC area exceeded the chance level even for participants who showed few measurable amplitudes (low-responsive participants). A possible implication is that a tonic increase in SC occurred in response to the relevant question even in low-responsive participants, who are traditionally excluded from analysis. The use of SC area might contribute to more impartial data evaluation and broader application of the CIT. These results indicate that SC area can be used as an alternative measure of SC in the CIT.

Psychology and the lie detector industry: A fifty-year perspective

Fifty years ago, in a trenchant analysis that challenged applied lie detection theory and science, David Lykken (1974) brought polygraphic interrogation methods to the attention of academia with the hope that these techniques would come under the purview of psychology and psychophysiology. In this perspective, I examine how this application of psychophysiology has evolved over the last half century and how its status has changed for 1) the comparison (control) question test (CQT), used in forensic applications; 2) polygraph screening tests, used to evaluate examinee integrity; and 3) the concealed information technique (CIT), used to assess recognition memory of crime details. The criticisms of the CQT and screening tests advanced by Lykken have been amplified and focused by the academic community over the last half century. However, this has had little effect on how these methods are practiced and has not curtailed their use. Although most private sector employee screening tests are now prohibited, personnel screening of government employees has increased, and screening tests of sex offenders are now commonplace. Even though the CIT has captured the interest of psychophysiologists as a scientifically defensible technique, its field use is negligible. A primary purpose of polygraphic interrogations continues to be the extraction of admissions and confessions. The lack of change in the polygraph testing status quo stems in large part from unwavering government support for the use of these methods. As a result, polygraph theory and research support continues to rest on shaky ground while practice continues unfettered by valid criticism.

Anterior N2 enhancement is not a general electrophysiological index of concealed information

Event-related potentials (ERPs) have been used with the concealed information test (CIT) to detect concealed recognition of specific stimuli (i.e., "probes"). While most research has focused on the P300 component, which is larger for infrequent probes than for frequent control stimuli (i.e., "irrelevants"), some studies have investigated an earlier ERP component, the anterior N2, with mixed results. Although some studies have reported a larger anterior N2 for probes than irrelevants (N2 enhancement), other studies, including our own, have not found such an effect. The present study aimed to replicate and extend our previous findings using the same CIT paradigm and measurement parameters. Results of Bayesian analyses show strong evidence against the hypothesis of anterior N2 enhancement by probes, replicating our previous work. Bayesian analyses also show strong evidence against the hypothesis of N2 enhancement for the three components revealed by a temporal principal component analysis (PCA) conducted to disentangle potentially overlapping ERP effects. In conclusion, whereas the CIT has shown promise in detecting recognition of specific information, anterior N2 enhancement cannot be used as an electrophysiological measure of concealed information across CIT paradigms.

Resistance of a short-term memory concealed information test with famous faces to countermeasures

The concealed information test (CIT) aims at identifying knowledge that a person wants to hide, by measuring physiological indices during the presentation of known versus unknown items. Recently, Lancry-Dayan et al. (Journal of Applied Research in Memory and Cognition, 7 (2), 291-302, 2018) proposed a new version of this test that included a short-term memory task to maximize differences between responses to items. Participants were asked to memorize four pictures of faces that included one face of an acquaintance. The authors observed that participants looked at the familiar face during the first second and then tended to avoid it. This specific orientation-avoidance pattern occurred even in participants instructed to conceal their familiarity with the known faces (in a spontaneous or a guided manner). In a first experiment, we reproduced Lancry-Dayan et al.'s (2018) study using photos of famous faces. The pattern found by Lancry-Dayan et al. was observed in participants asked to perform the memory task only, participants asked to conceal their familiarity with the famous faces, and participants of a countermeasure group. In a second experiment, we tested the robustness of Lancry-Dayan et al.'s countermeasure. We modified the instructions by emphasizing the oculomotor task or giving feedback. While between-group differences in gaze-pattern appeared after feedback was provided, classification analyses were still able to distinguish between familiar and unfamiliar faces accurately, which revealed the good resistance of this new CIT protocol to countermeasures.

Diagnosing eyewitness identifications with reaction time‑based Concealed Information Test: the effect of viewpoint congruency between test and encoding

Mistaken eyewitness identifications continue to be a major contributor to miscarriages of justice. Previous experiments have suggested that implicit identification procedures such as the Concealed Information Test (CIT) might be a promising alternative to classic lineups when encoding conditions during the crime were favorable. We tested this idea by manipulating view congruency (frontal vs. profile view) between encoding and test. Participants witnessed a videotaped mock theft that showed the thief and victim almost exclusively from frontal or profile view. At test, viewing angle was either congruent or incongruent with the view during encoding. We tested eyewitness identification with the RT-CIT (N = 74), and with a traditional simultaneous photo lineup (N = 97). The CIT showed strong capacity to diagnose face recognition (d = 0.91 [0.64; 1.18]), but unexpectedly, view congruency did not moderate this effect. View congruency moderated lineup performance for one of the two lineups. Following these unexpected findings, we conducted a replication with a stronger congruency manipulation and larger sample size. CIT (N = 156) showed moderate capacity to diagnose face recognition (d = 0.63 [0.46; 0.80]) and now view congruency did moderate the CIT effect. For lineups (N = 156), view congruency again moderated performance for one of the two lineups. Capacity for diagnosing face recognition was similar for lineups and RT-CIT in our first comparison, but much stronger for lineups in our second comparison. Future experiments might investigate more conditions that affect performance in lineups vs. the RT-CIT differentially.

Conditioning to true content and artificial intelligence in psychophysiological intention recognition

OBJECTIVE

The objective is to introduce a novel method for classical conditioning to true content (CtTC), and for the first time, apply this approach in the concealed information test (CIT) to effectively discern intentions. During CtTC, participants are trained to exhibit electrodermal responses whenever they recognize true content on a screen. Additionally, the objective is to evaluate a novel CIT-dataset preprocessing algorithm, employed to enhance machine learning (ML) classification performance.

METHODS

A total of 84 participants were evenly divided into four groups. Two groups of participants devised plans for stealing money from a supermarket, while the other two groups did not engage in any planning. One planning group and one non-planning group underwent CIT examination, while the remaining groups were subjected to CtTC.

RESULTS

The CIT accuracy initially stood at 52 % and increased to 71 % after Z-score and ML classification (McNemar test, p < 0.05). Conversely, the CtTC accuracy was 76 % and significantly improved to 93 % following Z-score and 95 % following ML classification (McNemar test, p < 0.05). In the best-performing classifiers, CtTC exhibited significantly superior metrics for guilty/innocent classification compared to CIT (Fisher's exact test, p < 0.05, power 1 - β > 0.90). In the CtTC group, reactivity and sensitivity significantly increased, indicated by higher EDR amplitudes (p < 0.05, two-tailed t-test, power 1 - β = 0.89) and the number of EDRs (p < 0.05, Fisher's exact test, power 1 - β = 0.90). There was no statistically significant difference between the Z-score and ML classification.

CONCLUSIONS

In the assessment of intentions, CtTC enhances both the sensitivity and accuracy of the CIT.

The role of response conflict in concealed information detection with reaction times

The concealed information test (CIT) presents various probe (familiar) items amidst irrelevant (unfamiliar) items. When the probe items appear, reaction time (RT) slows down. This RT-CIT effect has been accounted for by a conflict resulting from the need to deny familiarity of the familiar probes. The present pre-registered study (n = 292) examined whether response conflict is sufficient to account for the RT-CIT effect, using city and name items. Specifically, we compared the common conflict condition, where the response buttons emphasized familiarity of CIT items ("unfamiliar" versus "familiar"), to a novel no conflict condition, where the buttons emphasized categorical membership ("city" versus "name"). In line with our expectations, the RT-CIT effect was substantially stronger in the conflict condition; yet, it remained significant even in the no conflict condition. This implies a critical role for response conflict, but also suggests that other mechanisms (e.g. orientation to significant stimuli) may contribute to the RT-CIT effect.

Examining levels of processing using verbal & pictorial stimuli with the complex trial protocol in a mock theft scenario

The Complex Trial Protocol (CTP) is an EEG-based Concealed Information Test (CIT). Depth of processing influences memorability where deeper processing increases recollection. The CTP's performance as a function of shallow versus deep levels of processing has not been explored. Two experiments were conducted, one with verbal stimuli and the other with their pictorial referents. In both experiments, participants were randomly assigned to three groups, Innocent Control (Control) condition, Guilty Immediate Shallow Processing (Shallow) condition, and Guilty Immediate Deep Processing (Deep) condition. Shallow and Deep participants from both experiments underwent the same mock theft scenario and all three groups were later exposed to either a verbal (N = 41) or pictorial (N = 43) stimulus on a computer monitor. In the word study, no differences in CIT effect were found between any of the groups. Areas under the curve (AUCs) did not differ from chance (.624 and .679 for Shallow and Deep groups respectively). In the image study, the CIT effect for the Shallow and Deep groups differed from the Control one. The AUCs (.755 and .943 for the Shallow and Deep groups respectively) differed significantly from each other. Levels of Processing (LOP) did not appear to have any bearing on CTP performance when words were used as probes but did have an effect when images were used. The findings may hint at some of the limitations of the CTP and fail to replicate similar experiments, especially when words are used as probes, from the late Peter Rosenfeld's laboratory.

Does deception involve more cognitive control than truth-telling? Meta-analyses of N2 and MFN ERP studies

A number of psychological theories propose that deception involves more cognitive control than truth-telling. Over the last decades, event-related potentials (ERPs) have been used to unravel this question, but the findings are mixed. To address this controversy, two meta-analyses were conducted to quantify the results of existing studies reporting N2 or medial frontal negativity (MFN) associated with deception. In total, 32 papers consisting of 1091 participants were included, which yielded 32 effect sizes for N2 and 7 effect sizes for MFN. We found that deception was associated with a more negative N2 and MFN than truth-telling with medium and large effect sizes (r = .25 and .51, respectively). We also found that the deception paradigm modulated the results (p = .043), but found no evidence for publication bias. Our findings indicate that deception involves more cognitive control than truth-telling. Our review also identifies gaps in this literature, including a need for more ERP studies using spontaneous deception.

Ruling out feigned crime-related amnesia? A response to Acklin (2022)

In a recent paper, Acklin discussed a case of possible amnesia for a murder in terms of neurobiology, psychoanalysis, and personality assessment. Acklin accepted the defendant's claim of amnesia for the crime as genuine. The considerable literature that takes a skeptical view of crime-related amnesia was not cited, and the possibility of feigning or malingering was "ruled out" with a single sentence that does not withstand scrutiny. A review of the literature on feigned amnesia suggests that it may not be possible to rule out malingering even if the best available tools are used: There has been minimal investigation of most validity tests and estimates of base rates of feigned amnesia for a crime vary widely and make estimates of Negative Predictor Power highly unreliable. Although one cannot know from the information presented if Acklin's defendant legitimately experienced amnesia, feigning could not be ruled out using an interview and the test data cited by Acklin. I call for a moratorium on publication of further articles on crime specific amnesia that do not conscientiously examine other potential explanations and do not use current best practices for assessing negative response bias.

Reliability of the P3 component in a 3-stimulus concealed information test with known and unknown stimuli

The parietal P3 amplitude of the event-related potential (ERP) has been highlighted to signal stimulus salience in concealed information tests (CITs) with known and unknown stimuli. To extend previous validity investigations in deception research, the reliability of the early parietal P3 amplitude in a 3-stimulus CIT including known and unknown stimuli has been investigated in a sample of N = 68 participants. Variations of Cronbach's Alpha and split-half reliability (odd-even, 1st vs. 2nd half) of the early parietal P3 amplitude were considered for ERP quantification method (peak-to-peak, mean, baseline-to-peak), epoch selection strategies (chronological vs. random) and number of epochs (10-40) in three stimulus types (probe, target, irrelevant). Excellent reliability coefficients have been summarized for number of epochs, P3 quantifications, and epoch selection strategies. Moreover, the best-practice recommendations highlight mandatory combinations of epoch selection strategy, number of epochs and P3 quantifications to ensure robust and excellent reliabilities of the early parietal P3 amplitude in a 3-stimulus CIT with known (probe, target) and unknown (irrelevant) stimuli. The robustness of mandatory excellent reliability coefficients for the early parietal P3 has been discussed for two data tracks in single-case analyses.

A new theoretical perspective on concealed information detection

The concealed information test (CIT) was designed to detect concealed knowledge. It does so by measuring differential physiological and behavioral responses to concealed, compared to control, items - i.e., the CIT effect. Although the CIT has gained extensive empirical support in laboratory studies, scientific validity requires also a theoretical understanding of the method's underlying mechanisms. In this article, we present a new theoretical perspective. Specifically, we elaborate and clarify several features of Orienting Response (OR) theory, which has been the dominant theory in this domain. Importantly, we suggest for the first time that the voluntary (rather than the involuntary) OR modulates the CIT effect. Second, we argue that motivational-emotional accounts of the CIT effect are consistent with OR theory and cannot be considered as alternative approaches. Finally, we discuss some more recent developments which highlight the idea that different physiological measures reflect different underlying mechanisms - an idea dubbed as response fractionation.

Orienting versus inhibition: The theory behind the ocular-based Concealed Information Test

When trying to conceal one's knowledge, various ocular changes occur. However, which cognitive mechanisms drive these changes? Do orienting or inhibition-two processes previously associated with autonomic changes-play a role? To answer this question, we used a Concealed Information Test (CIT) in which participants were either motivated to conceal (orienting + inhibition) or reveal (orienting only) their knowledge. While pupil size increased in both motivational conditions, the fixation and blink CIT effects were confined to the conceal condition. These results were mirrored in autonomic changes, with skin conductance increasing in both conditions while heart rate decreased solely under motivation to conceal. Thus, different cognitive mechanisms seem to drive ocular responses. Pupil size appears to be linked to the orienting of attention (akin to skin conductance changes), while fixations and blinks rather seem to reflect arousal inhibition (comparable to heart rate changes). This knowledge strengthens CIT theory and illuminates the relationship between ocular and autonomic activity.

Interactive slide selection algorithm and machine learning in psychophysiological memory testing

Objective. To present a new type of concealed information test (CIT) that implements the interactive slide selection (ISS) algorithm and compare its effectiveness with a standard CIT (sCIT).Approach. The ISS algorithm presents slides interactively, based on the analysis of electrodermal activity, while sCIT presents slides in a predefined, sequential order. The algorithm automatically selects irrelevant, relevant, and control slides and presents them at the moment which is physiologically most suitable for electrodermal response detection. To compare the ISS-based CIT (issCIT) and sCIT, two objects, a bag, and a wallet, were presented to 64 participants, 32 of whomwere analyzed with sCIT, and another 32 with issCIT.Main results. The results show that ISS had significantly better true/false predictions (Fisher's exact test,p< 0.01). Also, the number of false positives (FPs) was significantly lower in the issCIT group in comparison with sCIT (Fisher's exact test,p< 0.001). Machine learning (ML) classifiers improved precision from 49% to 79% in the sCIT group (McNemar's test,p< 0.05), and from 85% to 100% in the issCIT group (McNemar's test,p< 0.05). The testing time in the issCIT group ranged between 42 and 107 s, while the average was 53 s. In the sCIT group, the testing time was always 330 s.Significance. Under the presented experimental settings, the ISS algorithm obtained significantly better classification results compared to sCIT, while the application of the ML algorithms managed to improve the classification results in both groups reaching a precision of 100%. The ISS algorithm allowed for a much shorter testing time compared to sCIT.

Effects of Mood on Psychophysiological Detection of Concealed Information and the Relation to Self-Assessed Lying Ability

The present study examined the effects of mood on physiological responses in the Concealed Information polygraph Test and the relation to self-assessed lying ability. One hundred and eight undergraduate students self-assessed their lie-telling ability, committed a mock theft, and were asked to conceal information related to the crime. Participants were then divided into three equal groups: two groups were asked to provide a detailed written account of either a happy or sad event in order to induce a happy or sad mood, while the third group served as a neutral group. Participants then underwent a polygraph test and were asked to try to avoid detection. An induced happy or sad mood tended to lower relative skin conductance responses to critical (crime related) items and enhance relative cardiovascular responses. Relative respiration responses to critical items obtained for the sad mood condition were more robust than the ones obtained for the happy mood condition. Under induced sad and happy moods, those who self-rated their lie-telling ability as high showed enhanced cardiovascular responsivity to critical items. These results were limited to the initial phase of the test. We discussed possible motivational explanations and implications for the Concealed Information polygraph test.

Brain fingerprinting field study on major, terrorist crimes supports the brain fingerprinting scientific standards hypothesis: classification concealed information test with P300 and P300-MERMER succeeds; comparison CIT fails

We conducted (I) 18 event-related potential (ERP) field tests to detect concealed information regarding major terrorist crimes and other real-world crimes and (II) 5 ERP tests regarding participation in a classified counterterrorism operation. This study is a test of the brain fingerprinting scientific standards hypothesis: that a specific set of methods for event-related potential (ERP) concealed information tests (CIT) known as the brain fingerprinting scientific standards provide the sufficient conditions to produce less than 1% error rate and greater than 95% median statistical confidence for individual determinations of whether the tested information is stored in each subject's brain. All previous published results in all laboratories are compatible with this hypothesis. We recorded P300 and P300-MERMER ERP responses to visual text stimuli of three types: targets contain known information, irrelevants contain unknown/irrelevant information, and probes contain the situation-relevant information to be tested, known only to the perpetrator and investigators. Classification CIT produced significantly better results than comparison CIT, independent of classification criteria. Classification CIT had 0% error rate; comparison CIT had 6% error rate. As in previous studies, classification-CIT median statistical confidences were approximately 99%, whereas comparison CIT statistical confidences were no better than chance for information-absent (IA) subjects (who did not know the tested information). Over half of the comparison-CIT IA determinations were invalid due to a less-than-chance computed probability of being correct. Experiment (I) results for median statistical confidence: Classification CIT, IA subjects: 98.6%; information-present (IP) subjects (who know the tested information): 99.9%; comparison CIT, IA subjects: 48.7%; IP subjects: 99.5%. Experiment (II) results (Classification CIT): error rate 0%, median statistical confidence 96.6%. Countermeasures had no effect on the classification CIT. These results, like all previous results in our laboratory and all others, support the brain fingerprinting scientific standards hypothesis and indicate that the classification CIT is a necessary condition for a reliable, accurate, and valid brainwave-based CIT. The comparison CIT, by contrast, produces high error rates and IA statistical confidences no better than chance.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-022-09795-1.

Diagnosing eyewitness identifications with reaction time-based concealed information test: the effect of observation time

Eyewitness identification procedures rely heavily on explicit identification from lineups. Lineups have been criticized because they have a considerable error rate. We tested the potential of implicit identifications in a Concealed Information Test (CIT) as an alternative. Previous experiments have suggested that implicit identification procedures might be suited when viewing conditions were favorable. In two experiments, mock eyewitnesses (Ns = 94, 509) witnessed a videotaped mock theft with longer or shorter observation time. We derived eyewitness identifications either implicitly from CIT reaction times or explicitly from simultaneous photo lineups. In Experiment 2, we also manipulated perpetrator presence. In both experiments, the perpetrator-present CIT showed capacity to diagnose face recognition, with large effect sizes (d_E1 = 0.85 [0.51; 1.18]; d_E2 = 0.74 [0.52; 0.96]), as expected. Unexpectedly, no moderation by observation time was found. In line with our hypothesis, no CIT effect emerged in the perpetrator-absent condition, indicating the absence of recognition (d_E2 = 0.02 [- 0.17; 0.20]). We found no compelling evidence that one method would outperform the other. This work adds to accumulating evidence that suggests that, under favorable viewing conditions and replication provided, the RT-CIT might be diagnostic of facial recognition, for example when witnesses are hesitant of making an explicit identification. Future work might investigate conditions that affect performance in one, but not the other identification method.

The promise of eye-tracking in the detection of concealed memories

There is a need for validated, theory-driven methods for memory detection. We review how physiological, neurophysiological, and oculomotor measures can be utilized to reveal concealed memories. Recent advances and future directions are discussed in light of the potential of eye-tracking to improve detection efficiency and resolve problems in real-world settings.

Selective memory detection: Context-dependent stimulus significance in the concealed information test

Previous studies have posited that the significance of a crime-relevant item in a question produces differential physiological responses in the Concealed Information Test (CIT). However, this term is equivocal and needs to be clarified in order to strengthen the theoretical underpinnings of the CIT. The present study examined the hypothesis that differential responding depends on the examinee's understanding of which item in a question is relevant to a given context. Participants performed a mock theft task, in which they were instructed to steal one item from each of two different locations. An identical CIT question asking about each stolen item was presented under different location contexts while skin conductance response, heart rate, and respiratory activity were recorded. Results indicated that only the relevant item specified by the context of the instruction elicited reliable differential physiological responses. This finding implies that differential responding in the CIT is flexible and context-dependent, and that specifying the subject of a given question is important for detecting crime-relevant memories in practical criminal investigations.

Belief or disbelief in feedback influences the detection efficiency of the feedback concealed information test

The feedback concealed information test (fCIT) is a new variant of the CIT that added feedback about participants’ concealing performances in the classical CIT. The advantage of the fCIT is that the resulting feedback related event-related potentials (ERPs) can be used to detect concealed information. However, the detection efficiency of feedback-based ERPs varies across studies. The present experiment examined whether the extent participants believed the feedback influenced their detection efficiency. Specifically, participants did a mock crime and were then tested in a fCIT. Following the fCIT, participants were asked to report how much they believed the feedback was accurate. Results showed that there were no significant correlations between the amplitude of the feedback related negativity (FRN), feedback P300, and participants’ self-report at the group level. However, individual analyses showed that the detection efficiency of both the FRN and feedback P300 were influenced by participants’ belief about the presented feedback. The detection efficiency of the FRN and the feedback P300 was higher among participants who believed the feedback. These findings suggest that the fCIT is dependent to some extent on the participants’ level of belief in the feedback.

A novel and effective item-source complex trial protocol: Discrimination of guilty from both knowledgeable and unknowledgeable innocent subjects

Innocent subjects who are knowledgeable of crime-related information will often be misclassified as "guilty" in P300-based complex trial protocol (CTP). Therefore, it is necessary to develop a more rigorous CTP that can effectively discriminate the guilty from both the knowledgeable and the unknowledgeable innocents. Sometimes the guilty and the knowledgeable innocents possess the same item memories but different source memories. The present study designed a novel item-source complex trial protocol based on the differences of source memory among the three kinds of individuals. Either the crime-related probe (e.g., the stolen ring) or one of the crime-unrelated stimuli (e.g., watch, earring, bracelet, or bangle) (item memory) was presented in the first part of each trail, and either a stealing-source word (e.g., stole) or other-source word (e.g., fetched) (source memory) was presented in the second part of each trail. The results showed that: (1) the P300 evoked by item memory could effectively discriminated the guilty from the unknowledgeable innocent (AUC = 0.76) but failed to effectively discriminate the guilty from the knowledgeable innocent (AUC = 0.60); (2) the late positive component evoked by source memory could effectively discriminated the guilty from both the knowledgeable innocent (AUC = 0.94) and the unknowledgeable innocent (AUC = 0.84) in one test.

Concealed identity information detection with pupillometry in rapid serial visual presentation

The concealed information test (CIT) relies on bodily reactions to stimuli that are hidden in mind. However, people can use countermeasures, such as purposely focusing on irrelevant things, to confound the CIT. A new method designed to prevent countermeasures uses rapid serial visual presentation (RSVP) to present stimuli on the fringe of awareness. Previous studies that used RSVP in combination with electroencephalography (EEG) showed that participants exhibit a clear reaction to their real first name, even when they try to prevent such a reaction (i.e., when their name is concealed information). Because EEG is not easily applicable outside the laboratory, we investigated here whether pupil size, which is easier to measure, can also be used to detect concealed identity information. In our first study, participants adopted a fake name, and searched for this name in an RSVP task, while their pupil sizes were recorded. Apart from this fake name, their real name and a control name also appeared in the task. We found pupil dilation in response to the task-irrelevant real name, as compared to control names. However, while most participants showed this effect qualitatively, it was not statistically significant for most participants individually. In a second study, we preregistered the proof-of-concept methodology and replicated the original findings. Taken together, our results show that the current RSVP task with pupillometry can detect concealed identity information at a group level. Further development of the method is needed to create a valid and reliable concealed identity information detector at the individual level.

The effect of mental countermeasures on a novel brain-based feedback concealed information test

The feedback concealed information test (fCIT) is a novel form of the CIT, providing participants with feedback regarding their memory concealment performance. The fCIT utilizes event-related potentials (recognition-P300 and feedback-related event-related potentials) and has been shown to provide high efficiency in detecting information concealment. However, it is unclear how well the fCIT performs in the presence of mental countermeasures. To address this question, participants were trained to use countermeasures during fCIT. Results showed that the recognition-P300 efficiency decreased when participants used countermeasures. However, the efficiencies of feedback-related negativity and feedback-P300 were unchanged, with feedback-P300 still showing a high detection efficiency (AUC = 0.86) during countermeasures. These findings demonstrate the potential of fCIT for subverting countermeasures.

Detecting concealed information using functional near-infrared spectroscopy (fNIRS) combined with skin conductance, heart rate, and behavioral measures

In this study, brain imaging data from functional near-infrared spectroscopy (fNIRS) associated with skin conductance response (SCR), heart rate (HR), and reaction time (RT) were combined to determine if the combination of these indicators could improve the efficiency of deception detection in concealed information test (CIT). During the CIT, participants were presented with a series of names and cities that served as target, probe, or irrelevant stimuli. In the guilty group, the probe stimuli were the participants' own names and hometown cities, and they were asked to deny this information. Our results revealed that probe items were associated with longer RT, larger SCR, slower HR, and higher oxyhemoglobin (HbO) concentration changes in the inferior prefrontal gyrus (IFG), middle frontal gyrus (MFG), and the superior frontal gyrus (SFG) compared with irrelevant items for participants in the guilty group but not in the innocent group. Furthermore, our results suggested that the combination of RT, SCR, HR, and fNIRS indicators could improve the deception detection efficiency to a very high area under the ROC curve (0.94) compared with any of the single indicators (0.74-0.89). The improved deception detection efficiency might be attributed to the reduction of random error and the diversiform underlying the psychophysiological mechanisms reflected by each indicator. These findings demonstrate a feasible way to improve the deception detection efficiency by using combined multiple indicators.

Speed versus accuracy instructions in the response time concealed information test

The response time concealed information test (RT-CIT) can reveal that a person recognizes a relevant item (probe) among other, irrelevant items, based on slower responding to the probe compared to the irrelevant items. Thereby, if this person is concealing knowledge about the relevance of this item (e.g., recognizing it as a murder weapon), this deception can be unveiled. In the present paper, we examined the impact of a speed versus accuracy instruction: Examinees (N = 235) were either presented with instructions emphasizing a focus on speed, with instructions emphasizing a focus on accuracy, or with no particular speed or accuracy instructions at all. We found that although participants responded to the probe and the irrelevants marginally faster when they had received instructions emphasizing speed, there was no significant difference between RTs of the different experimental groups and crucially no significant difference between the probe-irrelevant RT differences either. This means that such instructions are unlikely to benefit the RT-CIT, but it also suggests that related deliberate manipulation (focusing on speed on or accuracy) is unlikely to decrease the efficiency of the RT-CIT-contributing further evidence to the RT-CIT's resistance to faking.

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.

The Effect of Task-Irrelevant Emotional Valence on Limited Attentional Resources During Deception: An ERPs Study

Deception is a complex and cognitively draining dyadic process that simultaneously involves cognitive and emotional processes, both of which demand/capture attentional resources. However, few studies have investigated the allocation of attentional resources between cognitive and emotional processes during deception. The current study presented facial expressions of different valences to 36 participants. While an electroencephalogram was recording, they were asked to make either truthful or deceptive gender judgments according to preceding cues. The results showed that deceptive responses induced smaller P300 amplitudes than did truthful responses. Task-irrelevant negative emotional information (TiN) elicited larger P300 amplitudes than did task-irrelevant positive emotional information (TiP). Furthermore, the results showed that TiN elicited larger LPP amplitudes than did TiP in deceptive responses, but not in truthful ones. The results suggested that attentional resources were directed away to deception-related cognitive processes and TiN, but not TiP, was consistently able to compete for and obtain attentional resources during deception. The results indicated that TiN could disrupt with deception and may facilitate deception detection.

Different psychophysiological responses induced by a stimulus change during the orienting task and the Concealed Information Test

The orienting response (OR) account of the Concealed Information Test (CIT) posits that physiological responses to CIT items are components of the OR. Physiological variations within a stimulus sequence were investigated in an OR task (Study 1) and the CIT (Study 2). In Study 1, an unexpected increase in tone intensity was introduced after repeated standard tone presentations. The deviant tone elicited a large skin conductance response (SCR), heightened vascular tone, and self-reported surprise and also increased skin conductance level, self-reported arousal, and sustained vascular tone thereafter. In Study 2, the deviant relevant item presentation elicited a larger SCR and greater surprise compared with the frequent irrelevant item presentation, whereas vascular tone and self-reported arousal dropped after presentation of the relevant item. These results indicate that although phasic responses to a deviant stimulus were similar in both tasks, tonic variations following the stimulus change differed. Possible implications are discussed.

Countering information leakage in the Concealed Information Test: The effects of item detailedness

Concealed Information Tests (CIT) are administered to verify whether suspects recognize certain features from a crime. Whenever it is presumed that innocent suspects were contaminated with critical information (e.g., the perpetrator had a knife), the examiner may ask more detailed questions (e.g., specific types of knives) to prevent false positives. However, this may increase the number of false negatives if the true perpetrator fails to discern specific details from its plausible irrelevant controls, or because detailed crime‐scene information may be forgotten. We examined whether presenting items at the exemplar level protects against contamination, and whether it compromises the sensitivity in a physiological CIT. Participants (N = 142) planned a mock‐robbery, with critical items encoded either at the category or at the exemplar level. The CIT was administered immediately or after a 1‐week‐delay, with questions phrased at the categorical or exemplar level. There were no effects of time delay. Results revealed that when item detailedness was congruent at encoding and testing, the SCR, HR, and RLL showed larger differential responses, as compared with incongruent conditions. Participants contaminated with crime knowledge at the categorical level did not show a CIT‐effect for crime details at the exemplar level, suggesting detailed questions may counter the leakage problem. Asking questions at the exemplar level did not reduce the CIT detection efficiency as compared to asking questions at the categorical level. The importance of congruency between encoding and testing provides examiners with a challenge, as it is difficult to estimate how details are naturally encoded.

The Concealed Information Test (CIT) depends on the assumption that only guilty suspects have crime knowledge. As this assumption cannot always be met in real‐life, examiners may probe for more detailed information. We investigated whether use of detailed items affects accuracy in the CIT, and whether this depends on congruency between crime encoding and CIT testing. The current findings speak for the use of detailed questions.

The mechanism of filler items in the response time concealed information test

The response time concealed information test (RT-CIT) can reveal that a person recognizes a relevant (probe) item among other, irrelevant items, based on slower responding to the probe compared to the irrelevant items. Therefore, if this person is concealing the knowledge about the relevance of this item (e.g., recognizing it as a murder weapon), this deception can be unveiled. Adding familiarity-related filler items to the task has been shown to substantially increase the validity of the method, but assumptions for this effect have never been tested before. In the present series of three experiments (N = 511), we tested several factors, most of which were found to indeed influence the enhancing effects of fillers. First, larger enhancement is achieved when a smaller proportion of fillers shares the response key with the target. Second, familiarity context does play a role in the enhancement, and the target sharing its response key with the familiarity-referring fillers leads to larger enhancement. Third, mere symbolic fillers (such as simple arrow-like characters) also lead to enhancement, but filler words without task-relevant meaning are not effective. Fourth, small visual differences (lettercase or underlining) between fillers and the rest of the items have no significant influence. All this provides justification for the original structure of the fillers and also demonstrates that the enhancement is highly generalizable: Fillers have a potential to improve the RT-CIT regardless of deception scenario, item types, or the examinee's language comprehension.

Concealing Untrustworthiness: The Role of Conflict Monitoring in a Social Deception Task

Deception studies emphasize the important role of event-related potentials (ERPs) to uncover deceptive behavior based on underlying neuro-cognitive processes. The role of conflict monitoring as indicated by the frontal N2 component during truthful and deceptive responses was investigated in an adapted Concealed Information Test (CIT). Previously memorized pictures of faces should either be indicated as truthfully trustworthy, truthfully untrustworthy or trustworthy while concealing the actual untrustworthiness (untrustworthy-probe). Mean, baseline-to-peak and peak-to-peak amplitudes were calculated to examine the robustness of ERP findings across varying quantification techniques. Data of 30 participants (15 female; age: M = 23.73 years, SD = 4.09) revealed longer response times and lower correct rates for deceptive compared to truthful trustworthy responses. The frontal N2 amplitude was more negative for untrustworthy-probe and truthful untrustworthy compared to truthful trustworthy stimuli when measured as mean or baseline-to-peak amplitude. Results suggest that deception evokes conflict monitoring and ERP quantifications are differentially sensitive to a-priori hypotheses.

Challenging response latencies in faking detection: The case of few items and no warnings

Abstract

Faking detection is an ongoing challenge in psychological assessment. A notable approach for detecting fakers involves the inspection of response latencies and is based on the congruence model of faking. According to this model, respondents who fake good will provide favorable responses (i.e., congruent answers) faster than they provide unfavorable (i.e., incongruent) responses. Although the model has been validated in various experimental faking studies, to date, research supporting the congruence model has focused on scales with large numbers of items. Furthermore, in this previous research, fakers have usually been warned that faking could be detected. In view of the trend to use increasingly shorter scales in assessment, it becomes important to investigate whether the congruence model also applies to self-report measures with small numbers of items. In addition, it is unclear whether warning participants about faking detection is necessary for a successful application of the congruence model. To address these issues, we reanalyzed data sets of two studies that investigated faking good and faking bad on extraversion (n = 255) and need for cognition (n = 146) scales. Reanalyses demonstrated that having only a few items per scale and not warning participants represent a challenge for the congruence model. The congruence model of faking was only partly confirmed under such conditions. Although faking good on extraversion was associated with the expected longer latencies for incongruent answers, all other conditions remained nonsignificant. Thus, properties of the measurement and properties of the procedure affect the successful application of the congruence model.

Aging reduces EEG markers of recognition despite intact performance: Implications for forensic memory detection

ERP-based forensic memory detection is based on the logic that guilty suspects will hold incriminating knowledge about crimes they have committed, and therefore should show parietal ERP positivities related to recognition when presented with reminders of their crimes. We predicted that such forensic memory detection might however be inaccurate in older adults, because of changes to recognition-related brain activity that occurs with aging. We measured both ERPs and EEG oscillations associated with episodic old/new recognition and forensic memory detection in 30 younger (age < 30) and 30 older (age > 65) adults. EEG oscillations were included as a complementary measure which is less sensitive to temporal variability and component overlap than ERPs. In line with predictions, recognition-related parietal ERP positivities were significantly reduced in the older compared to younger group in both tasks, despite highly similar behavioural performance. We also observed aging-related reductions in oscillatory markers of recognition in the forensic memory detection test, while the oscillatory effects associated with episodic recognition were similar across age groups. This pattern of results suggests that while both forensic memory detection and episodic recognition are accompanied by aging-induced reductions in parietal ERP positivities, these reductions may be caused by non-overlapping mechanisms across the two tasks. Our findings suggest that EEG-based forensic memory detection tests are less valid in older than younger populations, limiting their practical applications.

Does hostile intent cause physiological changes? An airport security check simulation experiment

The present research was aimed at investigating in a simulation experiment whether the initiation of a hostile project in an environment akin to airport security checkpoints would translate in variation of cardiac activity. Twenty-three participants (eight women) enrolled as mock passengers had to make several traverses of a security checkpoint while carrying luggage containing either a neutral or a falsely dangerous item. The traverses with the falsely dangerous item were associated with an elevation of heart rate and higher drops of heart rate variability than the traverses with the neutral item. These effects were more salient for the first traverses. Implication of results for security management and the role of arousal and mental workload in threat detection are discussed.

Gaze-pattern similarity at encoding may interfere with future memory

Human brains have a remarkable ability to separate streams of visual input into distinct memory-traces. It is unclear, however, how this ability relates to the way these inputs are explored via unique gaze-patterns. Moreover, it is yet unknown how motivation to forget or remember influences the link between gaze similarity and memory. In two experiments, we used a modified directed-forgetting paradigm and either showed blurred versions of the encoded scenes (Experiment 1) or pink noise images (Experiment 2) during attempted memory control. Both experiments demonstrated that higher levels of across-stimulus gaze similarity relate to worse future memory. Although this across-stimulus interference effect was unaffected by motivation, it depended on the perceptual overlap between stimuli and was more pronounced for different scene comparisons, than scene–pink noise comparisons. Intriguingly, these findings echo the pattern similarity effects from the neuroimaging literature and pinpoint a mechanism that could aid the regulation of unwanted memories.

Reliability of the N2-component in a modified 3-stimulus concealed information test: On the importance of excellent measurement accuracy

Research on deception focused on the investigation of event-related potentials (ERP) to facilitate our knowledge on cognitive-motivational processes underlying deception. We investigated the reliability of the frontal N2 amplitude in a modified Concealed Information Test (CIT) (N = 64 participants). Variations of Cronbach's Alpha coefficients were examined for number of epochs per stimulus type, task modality and types of ERP quantification. Cronbach's Alpha coefficients of the N2 increased with the number of epochs across task modality, stimulus types and electrode positions. In a pictorial CIT, the frontal N2 indicated excellent Cronbach's Alpha coefficients (≥ 0.90) across electrode positions and quantification methods for 25 epochs per stimulus type. At least 15 epochs were necessary to achieve excellent Cronbach's Alpha coefficients (≥ 0.90) of the peak-to-peak N2 in a modified CIT across electrode positions and stimulus types. We provide best-practice advises for the necessity to assess N2 in a modified CIT with excellent reliability.

Brain-based concealed memory detection is driven mainly by orientation to salient items

In the pursuit of new methods for concealed memory detection, event-related potential components (ERP) have been placed at the forefront of research. No method, however, is scientifically complete without a theory and the present study therefore aimed to unravel the cognitive processes underlying these ERPs (i.e., orienting and arousal inhibition). This was accomplished by using a Concealed Information Test (CIT) in which participants were once motivated to conceal and once motivated to reveal their identity. The results showed a similarly strong P3 CIT effect in the two motivational conditions, which was enhanced for high salience compared to low salience identity items. Similar results were observed when using a multivariate machine-learning algorithm - suggesting that brain-based concealed memory detection is driven mainly by orientation to salient stimuli, rather than by arousal inhibition. In addition, the algorithm, trained and tested on the ERPs of different identity items, achieved detection rates exceeding those achieved by the P3. This implies that CIT researchers and practitioners could potentially rely on the entire ERP waveform instead of a-priori selecting separate components. Together these results enrich current understanding of the mechanisms underlying neurophysiological responding to concealed information and pave the way for novel and powerful algorithms which could be used in real-life forensic investigations.

Is the CIT susceptible to misleading information? A constructive replication

The Concealed Information Test (CIT) utilizes psychophysiological measures to detect crime-related knowledge in a suspect's memory. In other words, it can discriminate between knowledgeable (guilty) and unknowledgeable (innocent) suspects. The majority of CIT research is however conducted in controlled laboratory settings, which are more resistant to external influences than realistic forensic settings. Such influences include retroactive memory interferences which may threaten the validity of the CIT. One notable example is the misinformation effect - retroactive memory distortions caused by exposure to misleading information regarding a past event. The current study is a constructive replication of Volz et al. (J Forensic Sci 2017;63:1419) examining the effects of misleading information on the CIT. Participants underwent a three-stage experiment including a mock crime, exposure to misleading information, and a CIT. Results show that when misleading information was presented, explicit memory of the mock crime was reduced, but the physiological responses to the critical CIT items were only partially attenuated. This could suggest that the detection of crime-relevant information, using skin conductance and respiration measures, might be possible even when suspects are exposed to misleading information.

Dispersion matters: Diagnostics and control data computer simulation in Concealed Information Test studies

Binary classification has numerous applications. For one, lie detection methods typically aim to classify each tested person either as "liar" or as "truthteller" based on the given test results. To infer practical implications, as well as to compare different methods, it is essential to assess the diagnostic efficiency, such as demonstrating the number of correctly classified persons. However, this is not always straightforward. In Concealed Information Tests (CITs), the key predictor value (probe-irrelevant difference) for "truthtellers" is always similar (zero on average), and "liars" are always distinguished by a larger value (i.e., a larger number resulting from the CIT test, as compared to the zero baseline). Thereby, in general, the larger predictor values a given CIT method obtains for "liars" on average, the better this method is assumed to be. This has indeed been assumed in countless studies, and therefore, when comparing the classification efficiencies of two different designs, the mean difference of "liar" predictor values in the two designs were simply compared to each other (hence not collecting "truthteller" data to spare resources). We show, based on the meta-data of 12 different experimental designs collected in response time-based CIT studies, that differences in dispersion (i.e., variance in the data, e.g. the extent of random deviations from the zero average in case of "truthtellers") can substantially influence classification efficiency-to the point that, in extreme cases, one design may even be superior in classification despite having a larger mean "liar" predictor value. However, we also introduce a computer simulation procedure to estimate classification efficiency in the absence of "truthteller" data, and validate this procedure via a meta-analysis comparing outcomes based on empirical data versus simulated data.

Feedback does not influence the recognition-related P300 in a novel concealed information test while feedback-evoked P300 shows promising diagnostic accuracy

The feedback concealed information test (fCIT) is a novel variant of a CIT, which provides participants with feedback regarding their memory concealment performance during the CIT. Previous studies have found that feedback-related ERPs associated with feedback processing in the fCIT can accurately identify concealed information. However, it is still unknown whether the feedback influences the process and ERP signs of recognition during memory concealment, such as the recognition P300. To address this issue, the present study directly compared the recognition-based P300 in CITs with and without feedback. Results showed that the probe elicited a larger recognition P300 than irrelevants in both CITs with and without feedback, and there were no significant differences in recognition P300 between those two CITs. Moreover, the detection rate for recognition-based P300 in both CITs also had no significant difference. The feedback-related ERPs, especially feedback P300, continued to discriminate guilty and innocent subjects with AUCs well above the chance.

Concealed information revealed by involuntary eye movements on the fringe of awareness in a mock terror experiment

Involuntary eye movements during fixation are typically inhibited following stimulus onset (Oculomotor Inhibition, OMI), depending on the stimulus saliency and attention, with an earlier and longer OMI for barely visible familiar faces. However, it is still unclear whether OMI regarding familiarities and perceptual saliencies differ enough to allow a reliable OMI-based concealed information test (CIT). In a “mock terror” experiment with 25 volunteers, 13 made a concealed choice of a “terror-target” (one of eight), associated with 3 probes (face, name, and residence), which they learned watching text and videos, whereas 12 “innocents” pre-learned nothing. All participants then watched ~ 25 min of repeated brief presentations of barely visible (masked) stimuli that included the 8 potential probes, as well as a universally familiar face as a reference, while their eye movements were monitored. We found prolonged and deviant OMI regarding the probes. Incorporated with the individual pattern of responses to the reference, our analysis correctly identified 100% of the terror targets, and was 95% correct in discriminating “terrorists” from “innocents”. Our results provide a “proof of concept” for a novel approach to CIT, based on involuntary oculomotor responses to barely visible stimuli, individually tailored, and with high accuracy and theoretical resistance to countermeasures.

Eye spy a liar: assessing the utility of eye fixations and confidence judgments for detecting concealed recognition of faces, scenes and objects

BACKGROUND

In criminal investigations, uncooperative witnesses might deny knowing a perpetrator, the location of a murder scene or knowledge of a weapon. We sought to identify markers of recognition in eye fixations and confidence judgments whilst participants told the truth and lied about recognising faces (Experiment 1) and scenes and objects (Experiment 2) that varied in familiarity. To detect recognition we calculated effect size differences in markers of recognition between familiar and unfamiliar items that varied in familiarity (personally familiar, newly learned).

RESULTS

In Experiment 1, recognition of personally familiar faces was reliably detected across multiple fixation markers (e.g. fewer fixations, fewer interest areas viewed, fewer return fixations) during honest and concealed recognition. In Experiment 2, recognition of personally familiar non-face items (scenes and objects) was detected solely by fewer fixations during honest and concealed recognition; differences in other fixation measures were not consistent. In both experiments, fewer fixations exposed concealed recognition of newly learned faces, scenes and objects, but the same pattern was not observed during honest recognition. Confidence ratings were higher for recognition of personally familiar faces than for unfamiliar faces.

CONCLUSIONS

Robust memories of personally familiar faces were detected in patterns of fixations and confidence ratings, irrespective of task demands required to conceal recognition. Crucially, we demonstrate that newly learned faces should not be used as a proxy for real-world familiarity, and that conclusions should not be generalised across different types of familiarity or stimulus class.

Variation of picture angles and its effect on the Concealed Information Test

BACKGROUND

The reaction time-based Concealed Information Test (RT-CIT) is a memory paradigm used to detect crime-related knowledge. However, this would also imply that the RT-CIT would be vulnerable to factors that are known to compromise object recognition or memory integrity. From this perspective, one key issue is whether "guilty" memory can be detected if the crime-related images are photographed at different angles from what the perpetrator saw, which is almost always the case in the field. To investigate this, here we manipulated the deviation angles, from 0° to 330° in 11 steps, between the study and test phases to assess how the RT-CIT holds up against angular rotations.

RESULTS

We observed a robust RT-CIT effect at all deviation angles for both deep-encoders (Experiment 1) and shallow-encoders (Experiment 2). The RT-CIT was effective within the first 250 or so trials for both encoding groups, with smaller probe-irrelevant differences beyond that.

CONCLUSIONS

With appropriate encoding and memory strength, RT-CIT images do not necessarily have to match the exact angle of the perpetrator's perspective at the time of the crime. Unnatural angles such as 90° and 270° or unconventional rotational axes may require caution. Trial number under 250 trials show maximal Probe-Irrelevant difference, but more trials may add power to improve detection accuracy.

Time Passes Slowly When You Are Concealing Something

The item to be concealed elicits greater physiological arousal than other items. Since high physiological arousal causes an overestimation of time, the display duration of an item is expected to be perceived as longer when people intend to conceal it. After stealing and concealing one item, 36 university students were asked to judge the display duration of an item as shorter than, equal to, or longer than a memorised duration of 2 s. Pictures of three items including the stolen item were presented in the guilty condition, whereas pictures of three items that had not been stolen were presented in the innocent condition. The display of all items in the guilty condition was perceived as longer than in the innocent condition without difference between the concealed and other items. The intention to conceal increases tonic arousal reflected in a higher skin conductance level and leads to a non-specific temporal overestimation.