Michael R. Winograd

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 Complex Trial Protocol (CTP), was shown to be an improvement over the previous “three stimulus” P300‐based concealed information tests (CITs). Not only was it highly accurate with autobiographical information but was also resistant to the use of countermeasures (CMs). The current study applied the CTP to the detection of incidentally acquired information in a mock crime scenario. In previous “three stimulus” mock crime studies utilizing P300‐based CITs, participants memorized a guilty knowledge item(s). Special care was taken in the current study to ensure that participants' knowledge of the guilty item in the mock crime was obtained only during the commission of the act in order to bolster ecological validity. Overall, 92% of all participants in guilty, innocent, and countermeasure conditions were correctly classified. CM use was again indexed by reaction times (RTs).

Purpose. P300 memory detection test is a neuroscientific procedure to assess memories stored in the brain. P300 memory detection can and is currently applied to assess criminal suspects on recognition of critical crime information. Contrasting memory detection with lie detection, researchers have argued that P300 memory detection does not involve deception. We empirically investigated this argument by manipulating deception between groups. Methods. Thirty‐four community volunteers participated in a P300 memory detection test, answering either deceptively (deceptive condition) or truthfully (truth condition) to their own name. Results. P300 memory detection was significant in the truth condition, indicating that deceptive responding is not a prerequisite for valid P300 memory detection. However, there were clear indications that deceptive responding improved memory detection. Conclusions. Deception seems involved in the P300 memory detection test; and deceptive responding may add to test accuracy.

We recently introduced an accurate and countermeasure resistant P300-based deception detection test called the complex trial protocol (Rosenfeld et al. in Psychophysiology 45(6):906–919, 2008). When subjects use countermeasures to all irrelevant items in the test, the probe P300 is increased rather than reduced (as it was in previous P300-based deception protocols), allowing detection of countermeasure users. The current experiment examines the role of task demand on the complex trial protocol by forcing the subject to make countermeasure-like response to stimuli. Subjects made either a simple random button response to both probe and irrelevant stimuli (experiment 1) or a more complex, assigned, button response to probe and irrelevant stimuli (experiment 2). We found that an increase in task demand reduced the effectiveness of the test. Using random responses we found a simple guilty hit rate of 11/12 with no false positives, but only a 4/11 hit rate for countermeasure-users. Using assigned responses we found a simple guilty hit rate of 8/15 with no false positives, and a 7/16 hit rate for countermeasure-users. We herein suggest that the high level of task demand associated with these countermeasure-like responses causes reduced hit rates.

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.