Visual versus verbal: Assessing probe efficacy across modality and time delays in the Concealed Information Test

The Concealed Information Test (CIT), also known as the Guilty Knowledge Test (GKT), is a method of deception detection by presenting the suspects with familiar stimuli that only the culprits would recognize. Because recognition memory is crucial to the success of reaction time-based CIT, in this study we investigated how pictorial and verbal crime-related items (i.e., Probes) of a visually experienced mock crime would perform against time delay and memory deterioration. Participants visually encoded the details of a theft mock crime from a first-person perspective and were randomly assigned to one of the Probe modalities (i.e., verbal vs. pictorial) group and one of the time delays (immediate vs. 2-week delay) group: immediate verbal, immediate pictorial, 2-week verbal, 2-week pictorial. We observed significant Probe-Irrelevant RT difference in all 4 conditions. When we evaluated the ability of each condition to differentiate between guilty and innocent by calculating the area under the curve (AUC) with Receiver Operating Characteristic analysis, we observed a significant effect of time delay, with higher AUCs in the immediate condition compared to the 2-week delay, and no difference between verbal and pictorial modalities. Together, our results suggest that for visually experienced events, CIT effects can be observed 1) both with pictorial or verbal Probes, 2) both immediately and after 2 weeks, and 3) importantly, although pictorial and verbal Probes perform equally well, a 2-week delay would cost CIT efficacy in AUC.