The New Complex Trial Protocol for Deception Detection with P300: Mock Crime Scenario and Enhancements

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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

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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.

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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 Is into covert Ts.

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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

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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.

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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
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)

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Results (hit rates) from Rosenfeld et al. (2004)
Rosenfeld paradigm
Week BAD 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 BCD and BAD are 2
kinds of analytic bootstrap procedures.
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NEW COMPLEX TRIAL PROTOCOL (ctp)
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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 Ps 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.

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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) 11/12 (92) 12/12(
  100)
• Week 2 (CM) 10/11 (91) 11/12
  (92)
• Week 3 (no CM) 11/12 (92) 12/12
  (100)
• Main Study With false positive(FP) group.
•  
• Confidence.9
  Confidence.95
•  
• Test FPs Hits A
  FPs Hits A
• Iall .08 .92 .95
  0 .92 .98
• Imax 0 .92 .98
  0 .92 .98
•  

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EXP 1How does this CTP do in detecting
incidental mock crime details?

• Subjects were divided into three groups (n12)
• 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
  professors 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.

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A CTP Trial
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Results Grand Averages SG, CM, IC, all P
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Guilty Diagnoses

• Condition Detections Percentage
• SG 10/12
  83
• CM 12/12
  100
• IC 1/12
  8

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RTs to S1 (P or I)
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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.

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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 didnt, but we caught the CM users anyway.
• We have done other studies with non-random,
  explicitly assigned responses also.

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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).

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Results Grand Averages (Pz, 2 uV/ division)
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Detection rates

• Group BT/Iall.9 BT/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)
• These are screened via RT, which still nicely
  represents CM use within a block.

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New ERP P900the CM potential largest at Fz,
Cz (Pblack, Iallred, 2uV/division)
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New study Effects of various numbers of CMs,
1-5, with 5 total stimuli

• Elena Labkovsky Peter Rosenfeld

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GAs SG, IN, 1, 2, 3, 4, and 5 CN groups
SG 1CM 2CM 3CM 4CM 5CM
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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?

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A Mock Terrorism Application of the P300-based
Concealed Information Test Department of
Psychology, Northwestern University, Evanston, IL
60208-2700
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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 Iall Imax Imax Blind Imax Blind Imax
Guilty Innocent Guilty Innocent Guilty Innocent
1000 648 985 287 985 603
1000 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
999 586 908 217 907 565
985 690 888 382 886 706
912 390 667 129 698 650
903 644 837 215 842 702
966 546 863 289 872 619
12/12 0/12 12/12 0/12 10/12 0/12
AUC 1.0 AUC 1.0 AUC 1.0 AUC 1.0 AUC .979 AUC .979
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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.
• jp-rosenfeld_at_northwestern.edu