1. The New Complex Trial Protocol for Deception Detection with P300: Mock Crime Scenario and Enhancements
J. Peter Rosenfeld, John Meixner, Michael Winograd, Elena Labkovsky, Alex Haynes, Northwestern University

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

3. 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.

4. Old P300 Protocol
1 of 3 Stimuli on each trial: Probe (P), or Irrelevant(I), or Target (T). Subject presses either Target or Non-Target (NT) button. Both P and I can be Non-Targets. Special I is defined T.
This leads to 2 tasks for each stimulus:
1. implicit probe recognition vs.
2. explicit Target/Non-Target discrimination
Possible Result: Mutual Interference more task demand  reduced P300 to P. CMs hurt Old test.
A CM is an attempt to defeat the test by converting irrelevants into covert targets

5. How to do CMs:
When you see a specific irrelevant, SECRETLY make some 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.

6. 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
Guilty Group
Innocent Group
CM Group
9/11(82%)
1/11(9%)
2/11(18%)
Cross-Correlation(BC-AD) Method, p=.1
6/11(54%)
0/11(0%)
6/11(54%)

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

8. NEW COMPLEX TRIAL PROTOCOL (ctp)

10. 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; % 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.

11. Main Study: With false positive(FP) group.
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.
WEEK Hit Rate [Hit Rate]
Week 1 (no CM): /12 (92%) [12/12*( 100%)]
Week 2 (CM): /11 (91%) [11/12* (92%)]
Week 3 (no CM): /12 (92%) [12/12* (100%)]
Main Study: With false positive(FP) group.
Confidence= Confidence=.95
Test FPs Hits A’ FPs Hits A’
Iall
Imax

12. EXP 1:How does this CTP do in detecting incidental mock crime details?
Subjects were divided into three groups (n=12)
Simple Guilty (SG), Countermeasure (CM), and Innocent Control (IC)
All subjects first participated in a baseline reaction time (RT) test in which they chose a playing card and then completed the CTP using cards as stimuli.
SG and CM subjects then committed a mock crime.
Subjects stole a ring out of an envelope in a professor’s mailbox. Subjects were never told what the item would be, to ensure any knowledge would be incidentally acquired through the commission of the mock crime.
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.

13. A CTP Trial

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

15. Guilty Diagnoses Condition Detections Percentage SG 10/12 83
CM /
IC /

16. RTs to S1 (P or I)

17. Conclusions
As with autobiographical information, the CTP was found to be highly sensitive at detecting incidentally acquired concealed knowledge in a mock-crime scenario.
Detection rates using the CTP compare favorably to similar polygraph CITs. The main advantage of the CTP over the old P300 or polygraph CIT is its resistance to CM use. The traditional covert-response CMs used to defeat past P300 CITs were found to be ineffective against the CTP, and actually led to larger Probe-Irrelevant amplitude differences and detection rates.
CM use was also easily identified by a large increase in RT between the baseline and experimental blocks.

18. Exp. 2 Enhanced CTP with autobiographical information.
Since we saw in the previous experiment, and in Rosenfeld et al. (2008) that CMs actually lead to better detection, we thought we would incorporate explicit CM-like responses into the CTP protocol, in place of the “I saw it” S1 response.
So now we have a 5-button box for the left hand. The subject is instructed to press, at random*, one of the 5 buttons as the “I saw it” response to S1 on each trial with no repeats. T and NT (S2) stimuli and responses are as previously.
We also hoped that this would make CMs harder to do. It didn’t, but we caught the CM users anyway.
* We have done other studies with non-random, explicitly assigned responses also.

19. 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 Irrelevants: Say to yourself your first name the CM1, your last name as CM2. These are assigned prior to run.
Only one block per group (no baseline).

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

21. Detection rates: Group BT/Iall.9 BT/Imax.9
IC /13 (7.6%) /13 (7.6%)
CM /12 (100%) /12 (83%)*
*These are screened via RT, which still nicely represents CM use within a block.

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

23. Elena Labkovsky & Peter Rosenfeld
New study: Effects of various numbers of CMs, 1-5, with 5 total stimuli
Elena Labkovsky & Peter Rosenfeld

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

26. John Meixner & Peter Rosenfeld
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?

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

29. Table 1. Individual bootstrap detection rates
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.
Iall
Imax
Blind Imax
Guilty
Innocent
1000
648
985
287
603
610
999
416
998
602
955
598
889
476
892
649
996
611
898
430
893
605
994
150
946 17
943
689
909
475
698
284
761
547
945
600
677
365
702
536
997
555
959
250
961
569
586
908
217
907
565
690
888
382
886
706
912
390
667
129
650
903
644
837
215
842
966
546
863
289
872
619
12/12
0/12
10/12
AUC = 1.0
AUC = .979

30. 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.