Countermeasures to P300-based Guilty Knowledge Tests of Deception

1. Countermeasures to P300-based Guilty Knowledge Tests of Deception J.Peter Rosenfeld, Matt Soskins,Joanna Blackburn, & Ann Mary Robertson Northwestern University. Supported by DoDPI

2. Some History (earliest publications) • Rosenfeld et al., 1987,1988,1991 • Farwell and Donchin, 1991 • Allen, Iacono, & Danielson, 1992 • Johnson and Rosenfeld, 1992 • Since we were there at beginning, why do we challenge now with countermeasures? (1) It’s about time….

3. 2) Farwell’s web page, claiming 100% accuracy:

4. Stimuli: • Probes (P or R in figures): Items which subject is suspected of knowing (e.g., murder weapons). Subject denies(lies). • Targets (TR) Items: Items to which subject presses ‘YES’ . (Benchmark P300). • Irrelevants (I or W in figures): Items of which subject has no knowledge and denies, honestly, by pressing ‘NO’ .

5. How P300 amplitude is supposed to catch Liars: 1)P>I (‘BAD’) 2)P-TR corr >P-I corr(‘BC-AD’) 1)P=I 2)P-I corr >P-TR corr

6. Whither R-TR correlation if there are latency differences? Probe P3 Target P3 Nothing should happen to bootstrapped amplitude difference test (BAD) but bootstrapped cross-correlation test (BC-AD) should fail.

7. Experiment 1, based on Farwell & Donchin (1991): • --6 Different Probes • --Innocent, Guilty, and Countermeasure(CM) Groups • --Countermeasure: Associate various latent responses to different categories (jewelry type, drawer color, operation name, etc.), all irrelevant members of the category. • --”Off the Street “ subjects (Psych 101).

8. General Instructions…. • Mock crime scenario • Press “Yes” to Targets (on list) • Press “No” to all other stimuli (Possibly guilty probes and Irrelevants).

9. More simply…. • Probe Target I1 I2 I3I4ring bracelet necklace watch broach tiara • pink brown yellow purple red blue • donkey tiger lion cow pig horse • etc., etc…... (only half the matrix here.) • All these are shuffled, presented in random order, involving 4 repetitions of each item.

10. What are the covert countermeasures for the 6 categories of 6 probes? • 1) Jewelry category……….micro right finger wiggle • 2) drawer lining category…. “ left “ “ • 3) owner’s name category…. “ “ toe “ • 4) operation name category…” right “ “ • 5) location of item category…… Imagine professor slaps you • 6) desktop category……………Do Nothing • I.e., make irrelevants into relevant targets.

11. Guilty group: Probe(R) > Irrelevant (W). R > W

12. Guilty Group: TR vs R Both have P300

13. Innocent Group: R vs W Both lack P300

14. Innocent Group: TR vs R TR towers over P (R)

15. CM Group : R vs W No difference P(R) vs I (W)

16. CM Group: Tr vs R Target > Probe

17. Results, Exp. 1: CM works, and analysis method matters: 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%) --with “Off the street”subjects; see next 2 slides.

18. Guilty Subject, probe(R) vs irrelevant(W) R >> W: subject clearly guilty

19. …but clear latency shift in TR and R P300s ..so BC-AD fails, BAD catches the S.

20. Experiment 2: The one probe protocol (Rosenfeld et al., 1991). • 100% simpler to conceptualize: • There are 6 items, repeated 30-40 times randomly, consisting of.. • A probe, subject maybe guilty, • A target to force attention (not really necessary but allows us to test Farwell cross-correlation method vs. ours.) • 4 irrelevants.

21. Standard autobiographical oddball paradigm. • 6 dates are presented, one is the birth date. • 5 other dates with no personal significance, one is a target, four are irrelevant. • Subject is feigning head injury, the inability to recognize birth date 50% of the time, so he presses yes and no to all dates on 50-50 basis.

22. Design: • One group of advanced Ss run in 3 successive weeks. (Also Control group.) • Week 1: All naïve(about CM) and guilty (of having birth date and recognizing it despite overt lies. • Week 2: Use explicit countermeasure (to be explained). • Week 3: Repeat first week, stop the CM.

23. What’s the CM? • When you see the first Irrelevant, do micro left finger wiggle. • When you see second Irrelevant, do micro right toe wiggle. • When you see third irrelevant, imagine me slapping your face. • When you see fourth Irrelevant, do nothing. • I.e., make irrels. into rel. targets.

24. Results, week 1(guilty): Probe(R) vs.Irrelevant (W) As usual, R>>W

25. Week 1: Probe(R) and Target(TR): Both have nice P3

26. Week 2: Explicit CM, R v W Not so different anymore...

27. Week 3: 5/12 test beaters(effortless), R v W: Surprise! R = W

28. Week 3: 5/12 test beaters, R v TR--”classic defeats”: ..and TR >> R as with innocents.

29. Exp. 2; quantitative. • WKBADBC-AD • no CM 12/13(.92) 9/13(.69) • CM 6/12(.50) 3/12(.25) • no CM 7/12(.58) 3/12(.25) • (Control group: nothing much happened over 3 weeks of repeating week 1.)

30. RTs for 3 weeks; week 1= week 3, proving CM not usedin week 3.

31. Conclusions, bottom lines.. • 6-probe protocol beat-able, RT is no help, and the 6 probe combination lacks a real rationale anyway. (Lykken wouldn’t like?) • 1-probe protocol may be explicitly beat-able, but the very slow Irrelevant RT distribution will raise suspicions. 1 probe per run is more Lykkenable. • BUT---1-probe paradigm after CM practice is beat-able, period.

32. Farwell (SPR ‘08) didn’t agree:

33. But at the meeting, his letter, not he, showed up:

34. What to do? • Go to a new paradigm—the Complex Trial Protocol (Rosenfeld et al., 2008)