Variation of picture angles and its effect on the Concealed Information Test

Diagnosing eyewitness identifications with reaction time‑based Concealed Information Test: the effect of viewpoint congruency between test and encoding

Mistaken eyewitness identifications continue to be a major contributor to miscarriages of justice. Previous experiments have suggested that implicit identification procedures such as the Concealed Information Test (CIT) might be a promising alternative to classic lineups when encoding conditions during the crime were favorable. We tested this idea by manipulating view congruency (frontal vs. profile view) between encoding and test. Participants witnessed a videotaped mock theft that showed the thief and victim almost exclusively from frontal or profile view. At test, viewing angle was either congruent or incongruent with the view during encoding. We tested eyewitness identification with the RT-CIT (N = 74), and with a traditional simultaneous photo lineup (N = 97). The CIT showed strong capacity to diagnose face recognition (d = 0.91 [0.64; 1.18]), but unexpectedly, view congruency did not moderate this effect. View congruency moderated lineup performance for one of the two lineups. Following these unexpected findings, we conducted a replication with a stronger congruency manipulation and larger sample size. CIT (N = 156) showed moderate capacity to diagnose face recognition (d = 0.63 [0.46; 0.80]) and now view congruency did moderate the CIT effect. For lineups (N = 156), view congruency again moderated performance for one of the two lineups. Capacity for diagnosing face recognition was similar for lineups and RT-CIT in our first comparison, but much stronger for lineups in our second comparison. Future experiments might investigate more conditions that affect performance in lineups vs. the RT-CIT differentially.

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.