title: Increasing the number of irrelevant stimuli increases ability to detect countermeasures to the P300-based Complex Trial Protocol for concealed information detection.
abstract: We previously found that simultaneously executing a mental countermeasure and an explicit required response impairs reaction time (RT)-based detection of countermeasure use in a P300- based concealed information test. To address this issue, we increased the numbers of irrelevant stimuli to eight, and manipulated the proportions of to-be-countered irrelevant stimuli from 25% to 50% to 75% in three groups.
  
  
  RESULTS
  Based on P300 data, 100% of the simple guilty (no countermeasure use) and 92% of the innocent subjects were correctly identified as having or not having concealed information. In the countermeasure groups, detection rates varied from 71% to 92% across the different groups. Notably, in the present study with eight irrelevant items, simultaneous countermeasure use was indicated by elevated RT in the 50% and 75% countermeasure proportion groups, which it was not, previously, with 50% (two) countermeasures and four irrelevants.
authors.affiliation: Department of Psychology, Northwestern University, Evanston, Illinois 60208, USA. xiaoqinghu@u.northwestern.edu
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Hu
authors.forename: Daniel
authors.initials: D
authors.lastname: Hegeman
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Landry
authors.forename: J Peter
authors.initials: JP
authors.lastname: Rosenfeld
mesh_terms: D000293:Adolescent; D004569:Electroencephalography; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005260:Female; D006167:Guilt; D006801:Humans; D008014:Lie Detection; D008297:Male; D011930:Reaction Time / Q000502:physiology*; D055815:Young Adult