Impact of stimulus similarity between the probe and the irrelevant items during a card-playing deception detection task: The “irrelevants” are not irrelevant

Abstract

Event-related brain potential paradigms for the detection of concealed information commonly involve presenting probes embedded within a series of irrelevant items. This study investigated the impact of similarity of the irrelevant items with the probe. For the task, a card was shown followed by the sequential presentation of six "test" cards, one of which was the same as the initial card (the probe) along with five "irrelevant" cards that varied in terms of similarity with the probe. Participants either identified or denied recognition of the probe. The results show that P300 amplitude is modulated by stimulus similarity and highlight the importance of the irrelevant items on deception detection rates.

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

“…This could be due to the semantic saliency of the presented items: Autobiographical details may be more personally important and more rehearsed (leading to stronger memory traces), and hence the probes will be more salient, subjectively, compared to the irrelevant items. 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.…”

“…The inclusion of inducers did not improve the overall sensitivity of the method (probe-irrelevant P300pp differences) as we would have expected considering that these inducers (e.g., "mine" for familiar, or "unknown" for unfamiliar) probably increase awareness ITEM ROLES IN THE CTP CIT 27 of the denial of the recognition of the probe, and hence increase the subjective saliency of the probe items (Lukács, Kleinberg, et al, 2017). Nonetheless, the probe-irrelevant P300pp effects were lower for less personally important (low-salient) and higher for more personally important (high-salient) items as expected due to a similar reasoning, namely that the subjective saliency of the probe distinguishes it from the irrelevants, and the more the probe differs from the irrelevants, the larger the P300 differences will be (Marchand et al, 2013;Verschuere et al, 2015). While our results regarding semantic saliency are very clear, those regarding the inducers are less straightforward, and hence our explanations for the latter are somewhat speculative, serving primarily as hypotheses for further research.…”

“…The assertion (2) that a larger perceived difference between the oddball (in our case: probe) item and irrelevant items leads to larger P300 differencesin particular due to the task-relevance of the oddballhas long been demonstrated (see e.g. Johnson, 1986;Picton, 1992), and even directly in a P300-based CIT study (Marchand et al, 2013; see also Lukács et al, 2016). Finally, (3) effective semantic influences via inducer items correspond to semantic congruence effects in general.…”

“…: "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.…”

The first independent study on the complex trial protocol version of the P300-based concealed information test: Corroboration of previous findings and highlights on vulnerabilities

“…The recalling of the same word for these items of the larger group can also be described as giving them a common attribute, and thus making them overlapping. Consequently, the more the presented stimuli overlap with each other in their attributes, the smaller the P300 amplitude differences will be (Azizian et al, 2006;Marchand et al, 2013).…”