Presentation on theme: "Countermeasures to P300- based Guilty Knowledge Tests of Deception J.Peter Rosenfeld, Matt Soskins,Joanna Blackburn, & Ann Mary Robertson Northwestern."— Presentation transcript:
Countermeasures to P300- based Guilty Knowledge Tests of Deception J.Peter Rosenfeld, Matt Soskins,Joanna Blackburn, & Ann Mary Robertson Northwestern University. Supported by DoDPI
Countermeasure issues: zAmong the problems with both the ANS-based CQT and CIT raised by the report of the National Research Council of the National Academy of sciences (National Research Council, 2003) is the potential susceptibility of all ANS-based methods to countermeasures (CMs). As stated by (Honts, Devitt, Winbush, & Kircher, 1996, p. 84), ‘‘Countermeasures are anything that an individual might do in an effort to defeat or distort a polygraph test.’’ The National Research Council report went on to state that ‘‘Countermeasures pose a serious threat to the performance of polygraph testing because all the physiological indicators measured by the polygraph can be altered by conscious efforts through cognitive or physical means’’ (National Research Council, 2003, p. 4).National Research Council, 2003Honts, Devitt, Winbush, & Kircher, 1996, p. 84National Research Council, 2003, p. 4
ERPs to the rescue? zDeception researchers all hoped and indeed expected that when the P300 Event-Related EEG Potential was introduced as the dependent index of recognition in a CIT (Farwell & Donchin, 1991; Rosenfeld, Angell, Johnson, & Qian, 1991; Rosenfeld et al., 1988), the CM issue would be resolved. For example, the eminent inventor of the GKT / CIT, (Lykken, 1998, p. 293), suggested about CMs to P300 CITs: ‘‘Because such potentials are derived from brain signals that occur only a few hundred ms after the GKT alternatives are presented… it is unlikely that countermeasures could be used successfully to defeat a GKT derived from the recording of cerebral signals.’’ (Ben-Shakhar & Elaad, 2002, expressed a similar view.) All this optimism, as shown below, turned out to be misplaced.Farwell & Donchin, 1991Rosenfeld, Angell, Johnson, & Qian, 1991Rosenfeld et al., 1988Lykken, 1998, p. 293Ben-Shakhar & Elaad, 2002, expressed a similar view.
Some History (earliest publications) zRosenfeld et al., 1987,1988,1991 zFarwell and Donchin, 1991 zAllen, Iacono, & Danielson, 1992 zJohnson and Rosenfeld, 1992 zSince we were there at beginning, why do we challenge as late as 2003-4 with countermeasures? (1) It’s about time….
Stimuli used in 3-SP: z(1)Probes (P or R in figures): Items which subject is suspected of knowing (e.g., murder weapons). Subject denies(lies by pressing ‘NO’ ). z(2)Irrelevants (I or W in figures): Items of which subject has no knowledge and denies, honestly, by pressing ‘NO’. z(3) Targets (TR) Items: Irrelevant Items to which subject presses ‘YES’. (Benchmark P300).
We ultimately knew we could beat the test….. zIn the ordinary, un-countered 3-stimulus protocol, the subject is instructed to make unique responses to explicitly assigned targets which are readily executed with the typical result that large target P300s are evoked, since these targets are also rare and additionally, meaningful, due to their unique button requirement. (Rareness and meaningfulness are the major antecedents for P300; Johnson, 1986.)
IF….the subject can follow an experimenter’s instruction to respond uniquely to an experimenter- chosen irrelevant (an explicit target)… …….. then the subject could also covertly define some (or all) irrelevants for himself as implicit targets to which he could make unique responses. These originally irrelevant but now secret targets would also elicit large P300s so that one could no longer depend on the probe P300 amplitude to reliably exceed that of the irrelevant P300. * The larger probe P300 is, of course, what ordinarily makes the diagnosis of possession of concealed information.
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
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.
Experiment 1, based on Farwell & Donchin (1991) : z--6 Different Probes (“multiple probe protocol”) z--Innocent, Guilty, and Countermeasure(CM) Groups z--Countermeasure: Associate various latent responses to different categories (jewelry type, drawer color, operation name, etc.), all irrelevant members of the category.
General Instructions…. zMock crime scenario zPress “Yes” to Targets (on list) zPress “No” to all other stimuli (Possibly guilty probes and Irrelevants).
More simply…. zProbeTargetI1I2 I3 I4 ring bracelet necklace watch broach tiara zpink brown yellow purple red blue zdonkey tiger lion cow pig horse z etc., etc…... (only half the matrix here.) zAll these are shuffled, presented in random order, involving 4 repetitions of each item.
What are the covert countermeasures for the 6 categories of 6 probes? z1) Jewelry category……….micro right finger wiggle z2) drawer lining category…. “ left “ “ z3) owner’s name category…. “ “ toe “ z4) operation name category…” right “ “ z5) location of item category…… Imagine professor slaps you z6) desktop category……………Do Nothing zI.e., make irrelevants into relevant targets.
Results, Exp. 1: CM works, and analysis method matters: Diagnoses of Guilty Guilty Group Innocent Group CM Group 9/11(82%)1/11(9%) 2/11(18%) Amplitude Difference (BAD) method,p=.1 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.
Guilty Subject, probe(R) vs irrelevant(W) R >> W: subject clearly guilty
…but clear latency shift in TR and R P300s..so BC-AD fails, BAD catches the S.
Experiment 2: (“One probe protocol”) Rosenfeld et al., 1991). z100% simpler to conceptualize: zThere are 6 items, repeated 30-40 times randomly, consisting of.. zA probe, subject maybe guilty, zA target to force attention (not really necessary but allows us to test Farwell cross-correlation method vs. ours.) z4 irrelevants.
Standard autobiographical oddball paradigm. z6 dates are presented, one is the birth date. z5 other dates with no personal significance, one is a target, four are irrelevant. zSubject 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.
Design: zOne group of advanced Ss run in 3 successive weeks. (Also Control group.) zWeek 1: All naïve(about CM) and guilty (of having birth date and recognizing it despite overt lies. zWeek 2: Use explicit countermeasure (to be explained). zWeek 3: Repeat first week, stop the CM.
What’s the CM? zWhen you see the first Irrelevant, do micro left finger wiggle. zWhen you see second Irrelevant, do micro right toe wiggle. zWhen you see third irrelevant, imagine me slapping your face. zWhen you see fourth Irrelevant, do nothing. zI.e., make irrels. into rel. targets.
Results, week 1(guilty): Probe(R) vs.Irrelevant (W) As usual, R>>W
Week 1: Probe(R) and Target(TR): Both have nice P3
Week 2: Explicit CM, R v W Not so different anymore...
Week 3: 5/12 test beaters(effortless), R v W: Surprise! R = W
Week 3: 5/12 test beaters, R v TR--”classic defeats”:..and TR >> R as with innocents.
Exp. 2; quantitative. yWK BAD BC-AD zno CM 12/13(.92) 9/13(.69) zCM 6/12(.50) 3/12(.25) zno CM 7/12(.58) 3/12(.25) z(Control group: nothing much happened over 3 weeks of repeating week 1.)
RTs for 3 weeks; week 1= week 3, proving CM not used in week 3.
Conclusions, bottom lines.. z6-probe/ 3S protocol beat-able, and the 6 probe combination lacks a real rationale anyway. (Lykken wouldn’t like?) z1-probe/3S protocol may be explicitly beat-able, but the very slow Irrelevant RT distribution will raise suspicions. 1 probe per run is more Lykkenable. zBUT---1-probe paradigm after CM practice is beat-able, period.
But at the meeting, his letter, not he, showed up:
Cogn Neurodynamics DOI 10.1007/s11571-012-9230-0 zBrain fingerprinting field studies comparing P300-MERMER and P300 brainwave responses in the detection of concealed information zLawrence A. Farwell Drew C. Richardson Graham M. Richardson zPub. On line Dec 2012
Includes full “$100,000 Reward” (CM) Study. zBut: How does he know the CMs are really done??!! zThere are NO (Zip) Reaction Time data. zAnd the ERPs do not suggest CMs are being done.
Labkovsky & Rosenfeld (2011): Real CM effects on RT