Elena Labkovsky

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.

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 subjects 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 role of deception in P300 memory detection

Purpose. P300 memor yd etection test is an euroscientific procedure to assess memories stored in the brain. P300 memor yd etection can and is currently applied to assess criminal suspects on recognition of critical crime information. Contrasting memor yd etection with lie detection, researchers have argued that P300 memor y detection does not involv ed eception. We empirically investigated this argument by manipulating deception between groups. Methods. Thirty-four community volunteers participated in aP 300 memor y detection test, answering either deceptively (deceptiv ec ondition) or truthfully (truth condition) to their own name. Results. P300 memor yd etection was significant in the truth condition, indicating that deceptiv er esponding is not ap rerequisite for valid P300 memor yd etection. However, there wer ec lear indications that deceptiv er esponding improve dm emor y detection. Conclusions. Deception seems involved in the P300 memor yd etection test; and deceptiv er esponding ma ya dd to test accuracy.

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.

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.

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 participants 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.

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.

Effects of Motivational Manipulations on the P300-Based Complex Trial Protocol for Concealed Information Detection

Abstract This chapter reviews a series of experiments designed to explore the effects of financial incentive and instructions on the accuracy of the P300-based complex trial protocol. This protocol has been used in forensic (mock crime) scenarios, as well as in malingered memory-deficit scenarios seen in patients with closed head injury. Overall, it is seen that financial incentive does not influence the “CIT effect,” which is the difference between responses to critical versus noncritical stimuli.

Superiority of Pictorial Versus Verbal Presentation and Initial Exposure in the P300-Based, Complex Trial Protocol for Concealed Memory Detection

AbstractTwo 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.