Information Leakage in the Response Time‐Based Concealed Information Test

Abstract

The Response Time‐Based Concealed Information Test (RT‐CIT) can reveal when a person recognizes a relevant (probe) item among other, irrelevant items, based on comparatively slower responses to the probe item. For example, if a person is concealing his or her true identity, one can use the suspected identity details as probes, and other, random details as irrelevants. However, in our study, we show that even when participants are merely informed about such probes (i.e., the relevant identity details) before performing the RT‐CIT, their responses will also be slower to these details. Hence, it is more difficult to distinguish such innocent but pre‐informed persons from actually guilty persons. At the same time, we introduce a CIT version with familiarity‐related inducer stimuli, but with no targets, that elicits probe‐minus‐irrelevant RT differences only among guilty participants but not among informed innocent participants. Implications for the theory and the application of CITs are discussed.

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

“…This finding also implies a possibility to enhance the sensitivity of the method by increasing the distinctness between the primary and secondary tasks: For example, by displaying the secondary task items in lowercase or adding external marks to them (e.g., underline or frame). The specific effect of date items could also be further explored by testing the potential effect of dates as letter-only items (e.g., "JUNE NINE" vs. "JUNE 9"), or, conversely, presenting the inducers in a more visually similar format by appending random numbers to them (e.g., "MINE 19" or "OTHER 07," as discussed by Lukács & Ansorge, 2018b). However, a possible limitation is that the difference is never purely visual: The inherent circumstance that the inducers are meaningful makes them per definition semantically more similar to probe and irrelevant items regardless of appearance (e.g., in ITEM ROLES IN THE CTP CIT 30 contrast to using scrambled letters or letter-only nonwords in the secondary taskwhich could also be tested in future research).…”

“…We therefore ITEM ROLES IN THE CTP CIT 6 replace target number strings with self-referring items (expressions referring to the participants self-related, familiar details: "mine," "familiar"), and nontarget number strings with other-referring items (expressions referring to other, unfamiliar details, e.g. : "other," "irrelevant"; see also Lukács & Ansorge, 2018a, 2018b. Since (1) the perceived difference of the probe from the irrelevants is due to its meaning, and (2) a larger perceived difference leads to larger probe-irrelevant P300 differences (Lukács et al, 2016;Marchand, Inglis-Assaff, & Lefebvre, 2013), we hypothesized that (3) increasing this perceived semantic difference by using inducer targets would also lead to larger probe-irrelevant P300 differences, thereby increasing the sensitivity of the CTP CIT.…”

Dispersion matters: Diagnostics and control data computer simulation in Concealed Information Test studies

“…Previous simulation procedures had various implicit assumptions (i.e., unstated but necessary for the validity of the given procedure) about the SDs: (a) equal SDs in all experiments and designs when using standardized probe RT, reproducible by a specific randomized procedure [ 26 ], (b) control data SD equal to liar data SD [ 25 ], or (c) equal control data SDs in similar experimental settings [ 24 ]. It is logical that similar experiments lead to similar SDs, but the extent of similarity required would be difficult to estimate or test empirically.…”

CITapp - a response time-based Concealed Information Test lie detector web application

“…The basic framework of this application was first used in a recent online study; the resulting manuscript is currently under review (Lukács & Ansorge, 2019). An even more similar offline version is being used in a currently ongoing experiment.…”