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.

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

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

Financial Incentive Does Not Affect P300 in the Complex Trial Protocol (CTP) Version of the Concealed Information Test (CIT) in Malingering Detection. II. Uninstructed Subjects.

Well-known research showed that the skin conductance response (SCR) of the Autonomic Nervous System (ANS) in the Concealed Information Test (CIT) is usually augmented in participants who are financially and motivationally incentivized to beat the CIT. This is not what happens with Reaction Time (RT)-based CITs, P300 CITs based on the 3-stimulus protocol, nor on the P300-based complex trial protocol for detection of malingering (however these tests differ from forensic CITs). The present report follows up the Rosenfeld et al. (1, 2) study of motivated malingerers instructed how to beat the test, with uninstructed motivated (paid and unpaid) and unmotivated ("simple malingering") subjects, using episodic and semantic memory probes. The Test of Memory Malingering (TOMM) validated behavioral differences among groups. The "CIT effect" (probe-minus-irrelevant P300 differences) did not differ among incentive groups, although as previously, semantic memory-evoked P300s exceeded episodic memory evoked P300s. An effect of specific test-beating instructions was found to enhance the CIT effect for semantic information.

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.

Instructions to suppress semantic memory enhances or has no effect on P300 in a concealed information test (CIT).

The present study investigated the extent to which people can suppress semantic memory as indexed with the P300 ERP and the autobiographical implicit association test (aIAT). In EXP 1, participants (22) were run in a counterbalanced repeated measures study in both simply knowledgeable (SK) and knowledgeable with suppression (SP) conditions. A P300-based, concealed information test ("Complex Trial Protocol"; CTP) with a 50/50 Target/Nontarget (T/NT) ratio was given both with and without instructions to suppress semantic memories. The results showed increased P300s to probe name stimuli, reduced (but still high positive) aIAT d-scores, and increased simple reaction times to all stimuli used in ERP tests in the SP condition. EXP 2 was similar, but with SP and SK in two separate groups, and a 20/80 T/NT ratio. Again, ERP and aIAT results failed to show a suppression effect for semantic memory. The behavioral data suggest some task demand effects under suppression instructions, and that EXP 1 was more demanding than EXP 2.

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

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

Superiority of pictorial versus verbal presentation and initial exposure in the P300-based, complex trial protocol for concealed memory detection.

Two mock guilty groups had either pictorial or verbal initial exposure to crime items (probes) on which they were told they would later be tested. Then each subject was tested in two sessions on two successive days with both verbal and pictorial presentation, one test modality per session/day. The three dependent variables analyzed were three different estimates of the same basic measurement: the difference between P300s evoked by key (probe) and irrelevant stimuli. All three indexes were significantly increased more by both initial pictorial exposure, as well as by pictorial presentation modality, than by verbal exposure and presentation. We saw no main effect of exposure-presentation modality congruence, as congruence interacted with exposure: The largest probe-irrelevant differences were evoked by congruent pictorial exposure and presentation modality, and the smallest by congruent verbal exposure and presentation modality.

Evidence suggesting superiority of visual (verbal) vs. auditory test presentation modality in the P300-based, Complex Trial Protocol for concealed autobiographical memory detection.

One group of participants received a series of city name stimuli presented on trials of the Complex Trial Protocol (CTP) version of a P300-based, concealed information test (CIT). Stimuli were presented on alternating trials in either auditory or visual presentation modality. In 1/7 of the trials the participant's home town (probe) repeatedly appeared in a series of 6 other (irrelevant) repeated city names. In both modalities, probe stimuli produced larger P300s than irrelevant stimuli. Visual stimuli produced shorter behavioral reaction times and P300 latencies, as well as larger P300 probe amplitudes, probe-irrelevant amplitude differences, and individual diagnostic accuracies than the same stimuli presented in the auditory modality. Possible reasons for these effects are discussed, and subject to discussed limitations, the applied conclusion reached is that in all CITs, visual presentation of stimuli, if feasible, should be preferentially used.

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.

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.

P900: a putative novel ERP component that indexes countermeasure use in the P300-based concealed information test.

Countermeasures pose a serious threat to the effectiveness of the Concealed Information Test (CIT). In a CIT experiment, Rosenfeld and Labkovsky in Psychophysiology 47(6):1002-1010, (2010) observed a previously unknown positive ERP component at about 900 ms post-stimulus at Fz and Cz that could potentially serve as an index of countermeasure use. Here, we explored the hypothesis that this component, termed P900, occurs in response to a signal that no further specific response is required in a trial, and could thus appear in countermeasure users that respond differentially depending on the stimulus that appears. In the present experiments, subjects viewed four non-meaningful (irrelevant) dates and one oddball date. In three experiments, we examined P900's antecedent conditions. In the first, the unique item was a personally relevant oddball (the subject's birthdate). In a second, the unique item was a non-personally relevant oddball (an irrelevant date in a unique font color). In a third, all dates were irrelevant. We speculated that the presence of an oddball would not be necessary for P900. All participants made countermeasure-like responses following two specific irrelevant dates. As hypothesized, P900s were seen to non-responded-to irrelevant and oddball stimuli in all subjects but not to responded-to irrelevant stimuli, and the presence of an oddball was not necessary for elicitation of P900. This finding has potential application in deception settings-the presence of a P300 accompanied by the presence of a P900 in response to non-countered stimuli could provide evidence of incriminating knowledge accompanied by the attempt to use countermeasures to evade detection.

The P300-based, complex trial protocol for concealed information detection resists any number of sequential countermeasures against up to five irrelevant stimuli.

We previously tested the P300-based Complex Trial protocol for deception detection against 2 and 4 countered of 4 irrelevant stimuli. The protocol detected 90-100% of these subjects with <10% false positives. We have also shown that Reaction Time (RT) to the first trial stimulus is increased (group effect) with countermeasure use. We also reported a new P900 component associated with countermeasure use when 2 of 4 irrelevants are countered. In the present study we report data from 4 new groups and re-present for comparison previously collected data to have 7 groups: an innocent control, a guilty group not using countermeasures, and 5 guilty/countermeasure groups who counter from 1 to all 5 stimuli presented (4 irrelevants plus a probe). Subjects were detected at rates varying from 92 to 100% in the 6 guilty groups (n = 12 or 13 per group). There was 1 false positive in 13 innocent subjects. Additionally, 41 of 60 CM users were identified with RT as using countermeasures. P900 appeared in the 2 groups using 2 and 3 countermeasures.

A novel countermeasure against the reaction time index of countermeasure use in the P300-based complex trial protocol for detection of concealed information.

A P300 deception detection protocol was tested using simultaneous versus serial countermeasures and stimulus acknowledgment responses. Previously, P300 showed recognition and elevated reaction time identified countermeasure use. Probe-irrelevant P300 differences were significant in both countermeasure groups and control group. Detection rates were 11/12 for controls, 10/12 for serial countermeasure users, and 11/13 for simultaneous countermeasure users. Reaction time detected countermeasure use in serial responders, but not simultaneous responders. The simultaneous response reaction times were indistinguishable from controls.

New P300-based protocol to detect concealed information: resistance to mental countermeasures against only half the irrelevant stimuli and a possible ERP indicator of countermeasures.

Here, a rare probe or frequent irrelevant stimulus (S1) appeared in the first part of the trial, followed by either a target or nontarget (S2) in the second. Subjects randomly pressed one of five buttons to S1 to signal seeing it. Then they pressed one of two buttons for nontargets or targets. We tested three groups: simple guilty (SG), in which one stimulus was the subject's birth date (Probe); innocent (IN) in which all date stimuli were irrelevant; and Countermeasure (CM), like SG but subjects performed mental CMs to 2 of 4 irrelevants. Bootstrapped-based hit rates in the SG group=100%, based on probe versus all four averaged irrelevants (Iall), or based on probe versus RT-screened maximum irrelevant (Imax). In the IN group there was one false positive (8%, Probe vs. Iall) or none (0%, Probe vs. Imax). In the CM group, 100% were detected based on Probe versus Iall (92% based on Probe vs Imax). A new event-related potential at Fz and Cz at 900 ms indexed CM use.

The effects of asymmetric vs. symmetric probability of targets following probe and irrelevant stimuli in the complex trial protocol for detection of concealed information with P300.

The complex trial protocol (CTP, [J.P. Rosenfeld, E. Labkovsky, M. Winograd, M.A. Lui, C. Vandenboom & E. Chedid (2008), The complex trial protocol (CTP): a new, countermeasure-resistant, accurate P300-based method for detection of concealed information. Psychophysiology, 45, 906-919.]) is a sensitive, new, countermeasure-resistant, P300-based concealed information protocol in which a first stimulus (Probe or Irrelevant) is followed after about 1.4-1.8 s by a Target or Non-Target second stimulus within one trial. It has been previously run with a potentially confounding asymmetric conditional probability of Targets following Probes vs. Irrelevants. This present study compared asymmetric vs. symmetric conditional probability groups and found no significant differences in detection rates or Probe-minus-Irrelevant P300 differences between groups. Group differences were seen in error rates and reaction times (RT) to second stimuli. These differences were, however, not diagnostic for deception vs. truth-telling, and were attributable to response perseveration.

The Complex Trial Protocol (CTP): a new, countermeasure-resistant, accurate, P300-based method for detection of concealed information.

A new P300-based concealed information test is described. A rare probe or frequent irrelevant stimulus appears in the same trial in which a target or nontarget later appears. One response follows the first stimulus and uses the same button press regardless of stimulus type. A later second stimulus then appears: target or nontarget. The subject presses one button for a target, another for a nontarget. A P300 to the first stimulus indicates probe recognition. One group was tested in 3 weeks for denied recognition of familiar information. Weeks 1 and 3 were guilty conditions; Week 2 was a countermeasure (CM) condition. The probe-irrelevant differences were significant in all weeks, and percent hits were >90%. Attempted CM use was detectable via elevated reaction time to the first stimulus. In a replication, results were similar. False positive rates for both studies varied from 0 to .08, yielding J. B. Grier (1971) A' values from .9 to 1.0.