J. Peter Rosenfeld

Background: In applied psychophysiology, bootstrapping procedures are often used to classify individuals into one of two or more independent states (e.g., high risk vs low risk). Although the number of iterations required for a reliable bootstrap test is not universally agreed upon, some research (Rosenfeld et al., 2017b) suggests that 100 iterations is a sufficient number to obtain reliable results when analyzing P300 from a concealed information test. However, no study to-date has evaluated the diagnostic consistency of the 100 iterations test across repeated examinations. Methods: We evaluated the precision of the 100 iteration test by repeating the test 100 times per participant in a sample of 81 participants. The test was designed to classify participants as either knowledgeable or not knowledgeable of critical information related to a mock crime. Results: We found that the test provided variable classifications in approximately a quarter of our sample (n = 19/81 or 23%), specifically when a participant’s score presented near the diagnostic cutpoint. Moreover, the test’s diagnostic results varied by as much as +/-15%, in certain cases. Conclusion: Although the test provided reliable results for the majority of our sample, this was not true for a notable number of cases. We recommend that researchers report the variability of their diagnostic metrics and integrate this variability when classifying individuals. We discuss several simple examples of how to take variability into account when making classifications, such as by calculating the probability of one classification state over another given the data.

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.

One of the first things one learns in a basic psychology or statistics course is that you cannot prove the null hypothesis that there is no difference between two conditions such as a patient group and a normal control group. This remains true. However now, thanks to ongoing progress by a special group of devoted methodologists, even when the result of an inferential test is p > .05, it is now possible to rigorously and quantitatively conclude that (a) the null hypothesis is actually unlikely, and (b) that the alternative hypothesis of an actual difference between treatment and control is more probable than the null. Alternatively, it is also possible to conclude quantitatively that the null hypothesis is much more likely than the alternative. Without Bayesian statistics, we couldn’t say anything if a simple inferential analysis like a t-test yielded p > .05. The present, mostly non-quantitative article describes free resources and illustrative procedures for doing Bayesian analysis, with t-test and ANOVA examples.

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.

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

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.

Studies using the P300 ERP in detection of concealed information are reviewed. An overview of the initial findings, methodological issues, and use of bootstrapping methods for data analysis are considered, with various protocols explicated. Applications to forensic issues, employee screening, cognitive deficit malingering, and facial recognition in lineups are outlined. Countermeasures to the original P300‐based tests are described, and a possible approach to this problem using a new complex‐trial protocol is offered. Applications of this protocol to forensic and antiterror scenarios are then presented, along with its first independent replication. Studies of visual versus auditory stimulus presentation in the complex‐trial protocol are evaluated. Findings from attempted voluntary suppression of P300 as a recognition signal are presented, and the effects of motivational manipulations on the P300‐based complex‐trial protocol are summarized. Limitations of the research are reviewed, and, based on this review, future directions of P300 methods for detection of concealed information and deception are suggested that may guide the development of more precision and reliability of this promising tool.