Concealed identity information detection with pupillometry in rapid serial visual presentation

Abstract

The concealed information test (CIT) relies on bodily reactions to stimuli that are hidden in mind. However, people can use countermeasures, such as purposely focusing on irrelevant things, to confound the CIT. A new method designed to prevent the use of countermeasures, based on rapid serial visual presentation (RSVP), presents each stimulus on the fringe of awareness. Previous studies that used RSVP in combination with electroencephalography (EEG) showed that participants exhibit a clear reaction to their real first name, when they pretend to have a different name, even when they try to prevent such a reaction. Since EEG measures are not easily applicable outside the laboratory, we investigated here whether pupil size, which is easier to measure, is also able to detect concealed identity information. In our study, 31 participants were asked to adopt a fake name, and search for this name in an RSVP task, while their pupil sizes were recorded. Apart from this fake name, their real name and a control name also appeared in the task. We found that the pupil dilated more in response to the task-irrelevant real name, as compared to control names. However, while most participants showed this effect qualitatively, it was not statistically significant for most participants when analysed individually. Taken together, our results show that the current RSVP task with pupillometry can detect concealed identity information at a group level. Further development of the method is needed to create a valid and reliable concealed identity information detector at the individual level.