Increasing the ERP signal in the detection of guilty knowledge

Abstract

The N400 and P300, two event-related potentials (ERPs), were tested using a modified Guilty Knowledge Test for their effectiveness in discriminating people possessing guilty knowledge from those who did not. In the study phase, participants read different passages that detailed either a crime in a specific location (Guilty), some location, without a crime (Innocent but Knowledgeable) or an unrelated location without a crime (Naive). During EEG collection, participants viewed context phrases, some of which were relevant to the crime scene, and test words that were either congruent or incongruent to the context phrases. In Experiment 1, both Guilty and Innocent but Knowledgeable participants were originally classified as guilty because both produced large P300 amplitudes to the crimerelevant stimuli. However, few Innocent but Knowledgeable participants produced significant N400 amplitudes and thus were rejected as guilty in the final analysis.