P300 amplitudes in the concealed information test are less affected by depth of processing than electrodermal responses

Abstract

The Concealed Information Test (CIT) has been used in the laboratory as well as in field applications to detect concealed crime related memories. The presentation of crime relevant details to guilty suspects has been shown to elicit enhanced N200 and P300 amplitudes of the event-related brain potentials (ERPs) as well as greater skin conductance responses (SCRs) as compared to neutral test items. These electrophysiological and electrodermal responses were found to incrementally contribute to the validity of the test, thereby suggesting that these response systems are sensitive to different psychological processes. In the current study, we tested whether depth of processing differentially affects N200, P300, and SCR amplitudes in the CIT. Twenty participants carried out a mock crime and became familiar with central and peripheral crime details. A CIT that was conducted 1 week later revealed that SCR amplitudes were larger for central details although central and peripheral items were remembered equally well in a subsequent explicit memory test. By contrast, P300 amplitudes elicited by crime related details were larger but did not differ significantly between question types. N200 amplitudes did not allow for detecting concealed knowledge in this study. These results indicate that depth of processing might be one factor that differentially affects central and autonomic nervous system responses to concealed information. Such differentiation might be highly relevant for field applications of the CIT.

Item Roles Explored in a Modified P300-Based CTP Concealed Information Test

“…This is essentially the same reasoning as the one we presented for the potential benefits of inducers: The perceived difference of the probe from the irrelevants is due to its meaningfulness to the subject, and a larger perceived difference leads to larger probe-irrelevant P300 differences (Marchand et al, 2013). However, ITEM ROLES IN THE CTP CIT 9 in a more recent study (Gamer & Berti, 2012), it was argued that the difference between autobiographical and recently learned details is rather qualitative and ambiguous in view of saliency (confounded by memory type, self-relatedness, experimental context, etc. ).Therefore, these authors avoided such confounds by comparing semantically central and peripheral details from the same experimental mock-crime task (e.g., a stolen CD was central, while the office where this theft happened was peripheral).…”

“…To clearly delineate what we mean by semantic saliency in the present study, we can define it as a subjectively perceived importance (as also measurable via self-reported ratings) of items that otherwise belong to the same semantic dimension: For example, in our present experiment, these items were all self-related autobiographical details, and did not include any other types of potentially confounding details, such as crime-related ones recently learned in a mock-theft. The study of Gamer and Berti (2012) was similar in that they had also used items from the same semantic dimension (only crime details, while we used only autobiographical details). However, apart from our different experimental design (CTP CIT instead of regular CIT), the item categories were also different.…”

RT-based memory detection: Item saliency effects in the single-probe and the multiple-probe protocol.

“…In Experiment 2, the difference was much less pronounced: Only 1.15 points, representing a moderate effect. The data indicate that pronounced differences in item saliency affect the validity of RT-based memory detection and thereby extend item saliency effects from physiological measures (Carmel, Dayan, Naveh, Raveh, & Ben-Shakhar, 2003;Gamer & Berti, 2012;Gamer, Kosiol, & Vossel, 2010;Jokinen et al, 2006;Lieblich et al, 1976;Nahari & Ben-Shakhar, 2011;Peth, Vossel, & Gamer, 2012) to RTs. We think that the 21 use of an independent assessment of item saliency will be of great use in future research.…”

Concealed semantic and episodic autobiographical memory electrified

“…These differences in the paradigm clearly resulted in ERP differences compared with standard CIT results as, for example, there was no P3b effect. Furthermore, a subsequent CIT study by the same group (Gamer and Berti, 2012) failed to find any N2 effects. Although further work is required to fully characterize the factors that affect the frontal N2 in CIT paradigms, the current study shows that concealed information is not necessarily associated with a larger frontal N2 in CIT paradigms and that the literature is inconsistent.…”