Transcript The New Complex Trial Protocol for Deception Detection

J. Peter Rosenfeld, John Meixner,
Michael Winograd, Elena Labkovsky,
Alex Sokolovsky, Xiaoxing Hu,Alex
Haynes, Northwestern University
PROBE: GUILTY KNOWLEDGE ITEM: $5000
Press non-target button.
IRRELEVANT: OTHER AMOUNT: $200
Press non-target button.
TARGET: OTHER AMOUNT: $3000
Press target button.

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.

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




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.
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 CM Group
Guilty 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%)
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.

…If somebody beat the test?

Would he pay the $100,000?

No worries about that if you
are 100% confident that it
can’t happen (‘cuz you rigged
it!)


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.
P300 against the average of all
irrelevant

WEEK
Week 1 (no CM):
Week 2 (CM):
Week 3 (no CM):

Main Study: With false positive(FP) group.



Hit Rate
11/12 (92%)
10/11 (91%)
11/12 (92%)
[Hit Rate]
[12/12*( 100%)]
[11/12* (92%)]
[12/12* (100%)]


Confidence=.9
Confidence=.95





Test FPs Hits
A’
Iall .08 .92
.95
Imax 0
.92
.98
FPs
0
0
Hits
.92
.92
A’
.98
.98
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.

Condition
SG
CM
IC
Detections
10/12
Percentage
83
12/12
100
1/12
8
•
•
•
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.



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.
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 was the CM1, your last name
as CM2. These are assigned prior to run.
*Why 2 irrels? Meixner &Rosenfeld(2010) showed
countering all Irrels, not probe gives probe extra,
special significance. They did a study with only 5
irrels, one of which was not countered. It had big
P300. So doing CMs to all irrels is not a good strategy
from perp’s perspective.
*Why mental CMs? They should be faster and a bigger
challenge for our CTP.


Only one block per group (no baseline).

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.
Elena Labkovsky & Peter Rosenfeld
SG
1CM
2CM
3CM
4CM
5CM
P-Iall
7
6
5
4
P-Iall
3
2
1
0
SG
INN
1CM
2CM
3CM
4CM
5CM
John Meixner & Peter Rosenfeld
How do you catch bad guys before crimes
are committed, and before you know
what was done, where, when?
A Mock Terrorism Application of the P300-based Concealed Information Test
Department of Psychology, Northwestern University, Evanston, IL 60208-2700
Amplitude (µv)
12
Probe
Iall
8
4
0
Guilty
Innocent
Group
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
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
985
586
217
907
565
690
908
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 = .979


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.
[email protected]


Separated or split away from are
called “splitting CMs”.
What happens if subjects are
instructed to do CM and “I saw
it” response at the same time?
They lump these acts together.
This is called “Lumping CMs.”


Xiaoxing Hu to the rescue! (with
Dan Hegeman and Elizabeth
Landry).
He simply increased irrelevants
from 4 to 8, which should
increase demand and RT…


Remember, Allen Hu gave the
CMs to Ss in advance and let
them rehearse.
And his subjects were
geniuses, like you all…
 So
we are now working
with 10 Irrelevant
items… and 3,5,7 CMs.

… it is obvious that having
to form—on the spot-- and
hold 6 CMs for 6 of 8 Irrels
in your head –as must
happen in the field--is
probably too hard for most
bad guys to do.