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The New Complex Trial Protocol for Deception Detection with P300: Mock Crime & anti-terror ScenarioS PowerPoint Presentation
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The New Complex Trial Protocol for Deception Detection with P300: Mock Crime & anti-terror ScenarioS

The New Complex Trial Protocol for Deception Detection with P300: Mock Crime & anti-terror ScenarioS

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The New Complex Trial Protocol for Deception Detection with P300: Mock Crime & anti-terror ScenarioS

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  1. The New Complex Trial Protocol for Deception Detection with P300: Mock Crime & anti-terror ScenarioS J. Peter Rosenfeld, John Meixner, Michael Winograd, Elena Labkovsky, Alex Haynes, Northwestern University

  2. The Complex Trial Protocol is a brain-wave-based Concealed Information Test (CIT). • AKA—”Guilty Knowledge” Test. • Physiological responses accompany recognition of information known only by guilty perps and authorities. • Responses are traditionally Autonomic –HR, GSR—but we use brain waves:

  3. P300 Attributes: • An Endogenous, Event-Related Potential (ERP) • Positive polarity (down in Illinois). • Amp = f(1/[stim. Probability], meaningfulness)

  4. P300 at 3 scalp sites

  5. OLD 3-STIMULUS, P300-BASED CIT (GKT) PROBE: GUILTY KNOWLEDGE ITEM: $5000 Press non-target button. IRRELEVANT: OTHER AMOUNT: $200 Press non-target button. TARGET: OTHER AMOUNT: $3000 Press target button.

  6. Previous P300 DD protocols used Separate Probe(P),Irrelevant(I) and Target(T) trials. • 80% to 95% correct detection rates….but…. *Rosenfeld et al. (2004) and Mertens, Allen et al. (2008):These methods are vulnerable to Counter-measures (CMs) via turning I’s into covert T’s.

  7. How to do CMs: • When you see a specific irrelevant, SECRETLY make some specific response, mental/physical. • After all, if you can make special response to TARGET on instruction from operator, you can secretly instruct yourself. • Irrelevant becomes secret target. It makes big P300. If P = I, no diagnosis.

  8. Old “3 stimulus”P300 Protocol • 2 tasks for each trial: • 1. implicit probe recognition vs. • 2. explicit Target/Non-Target discrimination Hypothesized Result: Mutual Interference of 2 tasks more task demand  reduced P300 to P. CMs hurt Old test.

  9. Farwell’s web page, claiming 100% accuracy:

  10. Results from Rosenfeld et al. (2004): Farwell-Donchin paradigm (BAD and BCAD are 2 analysis methods.) Diagnoses of Guilty Amplitude Difference (BAD) method,p=.1 Innocent Group Guilty Group CM Group 1/11(9%) 9/11(82%) 2/11(18%) Cross-Correlation(BC-AD) Method, p=.1 0/11(0%) 6/11(54%) 6/11(54%)

  11. Results (hit rates) from Rosenfeld et al. (2004): Rosenfeld paradigm WeekBAD*BC-AD* 1: no CM 12/13(.92) 9/13(.69) 2: CM 6/12(.50) 3/12(.25) 3: no CM 7/12(.58) 3/12(.25) *Note: BC-AD and BAD are 2 kinds of analytic bootstrap procedures.


  13. New Complex Trial Protocol (CTP) • 2 stimuli, separated by about 1 s, per trial, • S1; Either P or I…..then…..S2 ; either T or NT. *There is no conflicting discrimination task when P is presented, so P300 to probe is expected to be as large as possible due to P’s salience, which should lead to good detection; 90-100 % in Rosenfeld et al.(2008) with autobiographical information. It is also CM resistant. (Delayed T/NT still holds attention.) * “I saw it” response to S1. RT indexes CM use.

  14. Main Study. Within-subject correct detections of guilty subjects based on bootstrap comparison of probe P300 against the average of all irrelevant P300s over 3 weeks. • WEEKHit Rate • Week 1 (no CM): 11/12 (92%) • Week 2 (CM): 10/11 (91%) • Week 3 (no CM): 11/12 (92%)

  15. EXP 1:How does this CTP do in detecting incidental mock crime details? • 3 groups (n=12) • Simple Guilty (SG), Countermeasure (CM), Innocent Control (IC) • All subjects first participated in a baseline reaction time (RT) test in which they chose a playing card. • SG and CM subjects then committed a mock crime. • Subjects stole a ring out of an envelope in a professor’s mailbox. • All subjects were then tested for knowledge of the item that was stolen. There were 1 P (the ring) and 6 I( necklace,watch,etc). • CM subjects executed covert assigned responses to irrelevant stimuli in an attempt to evoke P300s to these stimuli to try and beat the Probe vs. Irrelevant P300 comparison.

  16. A CTP Trial

  17. Results: Grand Averages: SG, CM, IC, all P

  18. Guilty Diagnoses • Condition Detections Percentage SG 10/12 83 CM 12/12 100 IC 1/12 8

  19. RTs to S1 (P or I)

  20. Conclusions • Unlike 3-SP, the CTP is highly sensitive at detecting incidentally acquired concealed knowledge in a mock-crime (as with autobiographical knowledge). • Another advantage of the CTP vs 3-SP or polygraph CIT: resistance to CM use. • CM use produces a large increase in RT between the baseline and test block, and within test block, probe vsirrelevant RT.

  21. Enhanced CTP with autobiographical information. • 5-button ‘I SAW it’ box. The subject is instructed to press, at random*, one of the 5 buttons. We hoped that this would make CMs harder to do. It didn’t, but we caught the CM users anyway.

  22. Design: • Autobiographical information (birthdates): One P and 4 I (other, non-meaningful dates). • 3 Groups as before: SG,CM, IC. • NEW: mental CMs to only 2 of the 4 Irrelevants: Say to yourself your first name OR your last name. These are assigned prior to run. • Only one block per group (no baseline).

  23. Results: Grand Averages (Pz, 2 uV/ division)

  24. Detection rates: • GroupBT/Iall.9BT/Imax.9 SG 13/13 (100%) 13/13 (100%) IC 1/13 (7.6%) 1/13 (7.6%) CM 12/12 (100%) 10/12 (83%) RT still nicely represents CM use within a block.

  25. New ERP: “P900—the CM potential” :largest at Fz, Cz(P=black, Iall=red, 2uV/division)

  26. RT results

  27. New study: Effects of various numbers of CMs, 1-5, with 5 total stimuli • Rosenfeld & Labkovsky

  28. GAs: SG, IN, 1, 2, 3, 4, and 5 CN groups

  29. Bar graph of previous slide

  30. A Mock Terrorism Study John Meixner & Peter Rosenfeld How do you catch bad guys before crimes are committed, and before you know what was done, where, when?

  31. Model of Terror Act Planning Scenario +Experimental guilty subjects come to lab and study 3 brochures dealing with pros & cons of 1) What CITY to attack, 2) What METHOD to use, 3) What DATE to attack on for later 3 blocks of CTP tests. + Then they write letter to boss with recommendations. + Innocent controls study vacation brochures, write recommendation letter to parents/room-mates.

  32. A Mock Terrorism Application of the P300-based Concealed Information Test Department of Psychology, Northwestern University, Evanston, IL

  33. Table 1. Individual bootstrap detection rates. Numbers indicate the average number of iterations (across all three blocks) of the bootstrap process in which probe was greater than Iall or Imax. Blind Imax numbers indicate the average number of iterations in which the largest single item (probe or irrelevant) was greater than the second largest single item. Mean values for each column are displayed in bold above detection rates.

  34. So…………. • CTP is a promising, powerful paradigm, against any number of CMs, mental and/or physical and RT reliably indicates CM use. The new “P900” might also. •

  35. But wait………Lumping CMs! • Instead of CM first, then I saw it response… • Do them simultaneously! Then Bye Bye RT index:

  36. Probe Iall

  37. But ERPs still work to catch ‘em! (Whewww!)