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Countermeasure mechanisms in a P300-based concealed information test
John B Meixner1, J Peter Rosenfeld
1Department of Psychology, Northwestern University, Evanston, Illinois 60208-2700, USA. jmeixner@northwestern.edu
Psychophysiology
|September 19, 2009
Summary
This study shows that omitting a response to a specific item can increase the P300 brainwave amplitude. This finding enhances deception detection by identifying individuals attempting countermeasures.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Forensic Science
Background:
- Previous P300-based deception detection tests are vulnerable to countermeasures.
- Countermeasures (CMs) typically aim to suppress P300 responses to relevant stimuli.
Purpose of the Study:
- To investigate the effect of omitting responses on P300 amplitude in a deception detection context.
- To assess the efficacy of a modified P300 test resistant to countermeasures.
Main Methods:
- Three groups were tested: guilty omit probe, innocent omit irrelevant, and guilty no omit.
- Participants responded to irrelevant items but omitted responses to specific probe items under different conditions.
- P300 amplitude was measured in response to probe stimuli.
Main Results:
- A significantly greater P300 amplitude was observed in the guilty omit probe group compared to other conditions.
- Omitting a response to a single stimulus, particularly a concealed information probe, enhances P300 amplitude.
- This 'omit effect' suggests a novel mechanism for detecting deception and CM use.
Conclusions:
- The P300-based deception detection test is resistant to countermeasures due to the 'omit effect'.
- Omitting responses can paradoxically increase, rather than decrease, the P300 response to critical stimuli.
- This research offers a more robust method for deception detection in forensic and security applications.
