Running Head: Scaled P300 Scalp Profiles in Detection of Deception

摘要

Three studies were performed. The first two dealt with countermeasures to brain wave-based detection of deception in concealed information test protocols. There are two kinds of such protocols extant. One, the '6-probe' protocol utilizes multiple different crime details whose brain responses are averaged together. This protocol was easily defeated in the first study, as the detection rates dropped from 82% detection in the simple guilty group to 18% in the guilty group using a countermeasure. Although the average reaction time distinguished these two groups, there was enough overlap in their reaction time distributions such that in any individual case, one could not use reaction time to infer deception. The second protocol, the '1-probe' protocol uses one crime detail as a probe in each of as many runs as one wishes. One group was run in three successive seeks as (1) a guilty group, (2) a countermeasure group, and (3) finally without the explicit use of the countermeasure. In the first week, 92% of the subjects were detected. The countermeasure dropped this rate to 50%. In the final third week, without explicit use of countermeasure, only 58% were detected. There was no overlap in the reaction time distributions of the first two weeks, suggesting that the explicit countermeasure use could be detected with reaction time. In the third week, the reaction time distributions looked like those of the first week, so that test beaters would not be detected with reaction time. Other matters examined were (1) a comparison of individual brain wave analysis methods; (2) a comparison of naive versus sophisticated subjects, and (3) a comparison in terms of workload between the 1-probe and the 6-probe protocols.