ODDBALL-EVOKED P300-BASED METHOD OF DECEPTION DETECTION IN THE LABORATORY .2. UTILIZATION OF NONSELECTIVE ACTIVATION OF RELEVANT KNOWLEDGE

We used a deception detection paradigm modeled on the type used for pre-employment screening procedures. Our novel dependent measure was P300 amplitude. Event-related potentials (ERPs) were recorded while subjects were presented with a list of eight antisocial acts one at a time, and one target-response phrase to which a 'yes' button press was required. Subjects were instructed to try to escape detection during the ERP test if they were guilty of any of the acts. After the ERP test, ground truth was established by the completion of an innocent/guilty check list of antisocial acts under perceived anonymous conditions tending to favor honest responding. Subjects were classified as innocent (n = 14) or guilty (n = 17) based on their check list response to the relevant act 'Used Falsified ID'. When comparing the P300 amplitudes in response to the relevant and to another act, we found that most group analyses revealed significant differences between guilty and innocent subjects. The subjects were also individually classified by a 3-step algorithm which involved: (1) a bootstrap amplitude test that compared the bootstrapped amplitudes of the P300s to the relevant and to another act; (2) relevant-to-target item P300 amplitude ratios; and (3) relevant act P300 amplitudes. Overall, the algorithm yielded 87% accuracy. The present study was intended to be an advance over our previous study (Rosenfeld, et al., 1991), in which we correctly classified 89% of the subjects using a similar P300-based deception detection paradigm. However, the possible confounding limitation of that study was that subjects had to complete an innocent/guilty check list of their antisocial acts prior to the ERP test. The present study investigated the accuracy of the P300-based test when subjects did not admit or selectively rehearse their guilt of the relevant act prior to the ERP test.