Association-based Concealed Information Test: A Novel Reaction Time-Based Deception Detection Method

The mechanism of filler items in the response time concealed information test

The response time concealed information test (RT-CIT) can reveal that a person recognizes a relevant (probe) item among other, irrelevant items, based on slower responding to the probe compared to the irrelevant items. Therefore, if this person is concealing the knowledge about the relevance of this item (e.g., recognizing it as a murder weapon), this deception can be unveiled. Adding familiarity-related filler items to the task has been shown to substantially increase the validity of the method, but assumptions for this effect have never been tested before. In the present series of three experiments (N = 511), we tested several factors, most of which were found to indeed influence the enhancing effects of fillers. First, larger enhancement is achieved when a smaller proportion of fillers shares the response key with the target. Second, familiarity context does play a role in the enhancement, and the target sharing its response key with the familiarity-referring fillers leads to larger enhancement. Third, mere symbolic fillers (such as simple arrow-like characters) also lead to enhancement, but filler words without task-relevant meaning are not effective. Fourth, small visual differences (lettercase or underlining) between fillers and the rest of the items have no significant influence. All this provides justification for the original structure of the fillers and also demonstrates that the enhancement is highly generalizable: Fillers have a potential to improve the RT-CIT regardless of deception scenario, item types, or the examinee's language comprehension.

Response Time Concealed Information Test on Smartphones

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 responding to the probe item. Thereby, if a person is concealing the knowledge about the relevance of this item (e.g., recognizing it as a murder weapon), this deception can be revealed. So far, the RT-CIT has been used only on desktop computers. In Experiment 1 (n = 72; within-subject), we compare the probe-irrelevant differences when using the conventional desktop-based CIT to using a smartphone-based CIT, demonstrating practical equivalence. In Experiment 2 (n = 116; within-subject), we demonstrate that using thumbs for responses (while holding the smartphone) leads to equally efficient CIT results as using conventional index finger responses. At the same time, this second experiment also demonstrates how smartphone-based studies may be efficiently run in large groups, using the participants’ own smartphones. Finally, as an interesting addition, here for the first time we also measured keypress durations (i.e., the time durations of holding down the response keys) in the RT-CIT, which we found to be significantly shorter for probe than for irrelevant items.

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

In this study, we introduced familiarity-related inducer items (expressions referring to the participant’s self-related, familiar details: “mine,” “familiar”; and expressions referring to other, unfamiliar details, e.g., “other,” “irrelevant”) to the Complex Trial Protocol version of the P300-based Concealed Information Test (CIT), at the same time using different item categories with various levels of personal importance to the participants (forenames, birthdays, favorite animals). The inclusion of inducers did not significantly improve the overall efficiency of the method as we would have expected considering that these inducers should increase awareness of the denial of the recognition of the probes (the true details of the participants), and hence the subjective saliency of the items (Lukács in J Appl Res Mem Cognit, 6:283–284, 2017a). This may be explained by the visual similarity of inducers to the probe and irrelevant items and the consequent distracting influence of inducers on probe-task performance. On the other hand, the CIT effect (probe-irrelevant P300 differences) was always lower for less personally important (low-salient) and higher for more personally important (high-salient) items.

Methodological improvements of the association-based concealed information test

The Association-Based Concealed Information Test (A-CIT) is a deception-detection method, in which participants categorize personally relevant items (e.g., their own surnames) as probes together with categorically similar but irrelevant items (e.g., others' surnames) by one key press A, while categorizing self-referring "inducer" items (e.g., "MINE" or "MY NAME") with an alternative key press B, thereby establishing an association between self-relatedness and B and an incongruence between the self-relatedness of probes and A (Lukács, Gula, Szegedi-Hallgató, & Csifcsák, 2017). The A-CIT's sensitivity to concealed information is reflected in an incongruence effect: slower responses to probes than to other surnames. To increase the relevance of categories, between trials of the original A-CIT, category-to-response mappings switched or repeated unpredictably. This, however, could have diminished incongruence effects, as the response labels were presented in the corners of the display, veering spatial attention away from the items at screen center. In the present online study (n = 294), we therefore tested two improved versions of the A-CIT that do not require spatial attention shifts to and from peripheral labels. One improved version presents per trial only one category label at screen center and requires comparison to the currently presented item. The other improved version is based on the Identification Extrinsic Affective Simon Task (ID-EAST), in which item categorization switches (or repeats) based on colors versus meanings of the central items. Both new versions outperformed the original A-CIT.