The Contribution of Mere Recognition to the P300 Effect in a Concealed Information Test

In two experiments, we investigated the role of mere recognition in a P300 based CIT. Mere recognition was isolated by having participants respond based on an irrelevant dimension of the stimuli. In Experiment 1 stimuli consisted of familiar and unfamiliar faces, with a dot placed on the left or the right cheeck. Participants responded according to dot location. In the second experiment, participants were presented with autobiographical information, alternated with irrelevant stimuli, while instructed to respond based on the case of the stimuli. Results showed that with both familiar faces, and autobiographical information, mere recognition was sufficient to elicit a P300.

Time and Encoding Effects in the Concealed Knowledge Test

Although the traditional “lie detector” test is used frequently in forensic contexts, it has (like most test of deception) some limitations. The concealed knowledge test (CKT) focuses on participants’ recognition of privileged knowledge rather than lying per-se and has been studied extensively using a variety of measures. A “guilty” suspect’s interaction with and memory of crimescene items may vary. Furthermore, memory for crimescene items may diminish over time. The interaction of encoding quality and test delay on CKT efficiency has been previously implied, but not yet demonstrated. We used a response-time based CKT to detect concealed knowledge from shallow and deep study procedures after 10-min, 24-h, and 1-week delays. Results show that more elaborately encoded information afforded higher detection accuracy than poorly encoded items. Although classification accuracy following deep study was unaffected by delay, detection of poorly elaborated information was initially high, but compromised after 1 week. Thus, choosing optimal test items requires considering both test delay and initial encoding level.     

The Concealed Information Test as an Instrument of Applied Differential Psychophysiology: Methodological Considerations

In this interpretative paper, I consider four sets of methodological issues that may be relevant to improving the concealed information test (CIT) as an instrument of applied differential psychophysiology. The first set has to do with psychophysiological measurement in the CIT (e.g., specific sensitivity testing in lab vs. field). Secondly, I consider the relationships between the psychological process of deception and the CIT. Thirdly, I consider the problem of laboratory-to-field generalization of the CIT, a consideration that includes a discussion of whether the lab/field differences are merely quantitative or actually qualitative. Finally, I discuss theories concerning the hypothetical mechanisms underlying the CIT, and argue that while the purely cognitive, Sokolovian, orienting response (OR) account is widely accepted as the sole mechanism, there is evidence to suggest that not just motivational, but even emotional mechanisms are also relevant.

Detecting Concealed Knowledge Using a Novel Attentional Blink Paradigm

Traditional concealed information paradigms rely on the idea that stimuli that are meaningful to a person (critical items) will draw attentional resources disproportionately, relative to stimuli that are not (irrelevant items), generating detectable differences on a suitable dependent variable (behavioral, psychophysiological, or neural). Here, we introduce a behavioral paradigm that could be used to reveal concealed information by exploiting the link between concealed information and attentional processes more directly. This novel paradigm is based on the attentional blink phenomenon in which detection of a stimulus reduces detection accuracy rates of subsequent target stimuli within a 200–500 ms time window. We hypothesized that a well-known face used as a critical item could capture attentional resources automatically, making it harder to detect the occurrence of a subsequently presented target face. The results confirmed this hypothesis, and showed that concealed knowledge of a famous face could be detected in 9 out of 12 individuals by looking for a relative dip in target detection accuracy after the presentation of a critical item.     

The Role of Intention to Conceal in the P300-based Concealed Information Test

The present study examined whether intention to conceal knowledge affects P300 amplitude and detection accuracy in the concealed information test. Eighteen university students were told to choose one card from five and to hide it. In the conceal condition, participants made an effort to leave their chosen card undetected by suppressing their brain response to it. In the transmit condition, they attempted to inform the experimenter of the chosen card by enhancing brain response to it. In the no secret condition, participants showed the chosen card to the experimenter beforehand and lost their motivation to conceal it. The difference in P300 amplitude between the chosen and unchosen cards was significant only in the conceal and transmit conditions. The results suggest that a larger P300 amplitude for the chosen card was not due to a deception-specific process but rather to increased significance of the item caused by additional processing.