title: P900: a putative novel ERP component that indexes countermeasure use in the P300-based concealed information test.
abstract: Countermeasures pose a serious threat to the effectiveness of the Concealed Information Test (CIT). In a CIT experiment, Rosenfeld and Labkovsky in Psychophysiology 47(6):1002-1010, (2010) observed a previously unknown positive ERP component at about 900 ms post-stimulus at Fz and Cz that could potentially serve as an index of countermeasure use. Here, we explored the hypothesis that this component, termed P900, occurs in response to a signal that no further specific response is required in a trial, and could thus appear in countermeasure users that respond differentially depending on the stimulus that appears. In the present experiments, subjects viewed four non-meaningful (irrelevant) dates and one oddball date. In three experiments, we examined P900's antecedent conditions. In the first, the unique item was a personally relevant oddball (the subject's birthdate). In a second, the unique item was a non-personally relevant oddball (an irrelevant date in a unique font color). In a third, all dates were irrelevant. We speculated that the presence of an oddball would not be necessary for P900. All participants made countermeasure-like responses following two specific irrelevant dates. As hypothesized, P900s were seen to non-responded-to irrelevant and oddball stimuli in all subjects but not to responded-to irrelevant stimuli, and the presence of an oddball was not necessary for elicitation of P900. This finding has potential application in deception settings-the presence of a P300 accompanied by the presence of a P900 in response to non-countered stimuli could provide evidence of incriminating knowledge accompanied by the attempt to use countermeasures to evade detection.
authors.affiliation: Department of Psychology, Northwestern University, Evanston, IL, USA. jmeixner@northwestern.edu
authors.forename: John B
authors.initials: JB
authors.lastname: Meixner
authors.forename: Elena
authors.initials: E
authors.lastname: Labkovsky
authors.forename: J Peter
authors.initials: JP
authors.lastname: Rosenfeld
authors.forename: Michael
authors.initials: M
authors.lastname: Winograd
authors.forename: Alexander
authors.initials: A
authors.lastname: Sokolovsky
authors.forename: Jeff
authors.initials: J
authors.lastname: Weishaar
authors.forename: Tim
authors.initials: T
authors.lastname: Ullmann
mesh_terms: D000293:Adolescent; D002540:Cerebral Cortex / Q000502:physiology*; D003265:Contingent Negative Variation / Q000502:physiology*; D008192:Deception; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008014:Lie Detection; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D055815:Young Adult