Project Final Presentation
Enhanced Lie Detector
By: Lander Shiran and Balaban Nir
Supervisor: Lange Danny
Project Goals
Characterizing signals from the
human body, and decides whether
the person told the truth.
 The project is an extension of the
regular lie detector but it uses other
methods for decision.

Description
Comparing signals from both sides.
 The right hand indicates the arousal
of the left hemisphere and the left
hand, the right hemisphere.

Theoretical Overview – Left and
Right Brain Split
The brain is divided into two parts:
the left and the right.
 In the left part of the brain, logical,
verbal and sequential thoughts are
processed.
 The right part is responsible for
emotional, non-verbal thoughts and
feelings.

Theoretical Overview
Truth
False
• The left lobe is
• Both lobes are
aroused and the
aroused similarly.
right is suppressed.
• The right and the
left lobes are working • The right lobe is
closer to reality and
together
only the left brain
synchronically.
can make up new
facts – lie.
The ECG Machine
The ECG machine monitors the signal
from the subject body to digital
signals in the computer, there we can
process them as we find fit.
The machine have number of detectors
that should be attached to the body
in the right places.
The Questionnaire – Calibration
Phase
In order to recognize a lie, we must
first characterize the truth.
That is why the calibration phase
exists: we ask the subject 10
questions and get 10 true answers.
The lie will deviate from the truth
“section”.
The Questionnaire – Examination
Phase
1.
2.
3.
The subject will write down the
true answers and keep them for
himself.
The subject will answer the
investigators, while monitored
by the ECG machine and will try
to “fool” it by telling lies.
The subject will give the
prewritten answers to the
investigators.
The Questionnaire – Goals
1.
2.
3.
Because the subject writes down the
answers, he cannot regret  more
pressure .
We use the practice of “the carrot and
the stick” : “anybody who will fool the
machine will get a pizza”  a motive.
We finally get a database of signals that
can be organized by true & false.
Measurements – Electrodes
Positions
The ideal scenario:
We would like two
clean signals from
both sides of the
body – 2 common
are needed.
Common
Channel
Measurements – Electrodes
Positions
The symmetric scenario:
The common will be
placed in the middle of
the body and will
create symmetric
signals.
Common
Channel
Measurements – Electrodes
Positions
The a - symmetric scenario:
The common will be
placed on one of the
hands so we’ll get one
noisy channel and one
clean channel.
Common
Channel
Measurements – The Signals
The a - symmetric scenario:
At each question
we will wait for
15 sec before
presenting the
question so that
the subject
relaxes.
Left hemisphere - noised signal
1500
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5
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sec
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Right hemisphere - clean signal
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15 sec
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sec
Preprocessing The Signals
1.
2.
Because we have one clean signal and
one noisy signal we must filter them in
order to compare them.
The ECG signal is of greater frequency
from the data and therefore we use LPF
on both signals (the same delay).
Some signals were taken out of the
database because the subject was not
aroused as expected.
Preprocessing The Signals
3. Taking only the appropriate interval, from the
15 sec until the signal fades.
In order to achieve that a designated GUI
was created:
Preprocessing The Signals
8 sec
LP Filter
Analyzing The Signals Parameters
Goal – finding parameters that will
indicate whether or not the subject
lied.
List of examined parameters:
 K parameter – indicates the ratio
between the left hemisphere signal
and the right one.
We calculated the K by :
. k  arg min { Left  k  right }
k
Analyzing The Signals Parameters
2. Energy difference - in order to find the
dominant hemisphere the difference
between the two hemispheres
energies is calculated:
Dif  Left  Right
Analyzing The Signals Parameters
3. Correlation – assuming that when a subject
tells the truth, his two hemispheres work
respectively and when a subject lies, the
harmony ceases.
4. Delay between peaks – according to the
article, there may be a delay between the
reaction of the hemispheres.
The delay was calculated according to the
peaks.
Analyzing The Signals –
Parameters Examples
We use two methods for analyzing the
parameters:
1. Parameter vs. Question number :
corr
1
0.8
0.6
corr
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Analyzing The Signals –
Parameters Examples
We use two methods for analyzing the
parameters:
2. Parameter 1 vs. Parameter 2 :
corr vs. k
k
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k
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corr
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corr
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0
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k
2
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0
10
Analyzing The Signals – Pattern
Recognition
PCA – Principal Component Analyze
PCA involves a mathematical procedure
that transforms a number of correlated
variables into a number of uncorrelated
variables (not necessarily what we want)
called principal components. The first
principal component accounts for as much
of the variability in the data as possible, and
each succeeding component accounts for
as much of the remaining variability as
possible.
Analyzing The Signals – Pattern
Recognition
PCA – Principal Component Analyze
PCA
Analyzing The Signals – Pattern
Recognition
Questionnaire
PCA
PCA
PCA
PCA
Analyzing The Signals – Pattern
Recognition
Questionnaire
PCA
PCA
Do you like beer?
Yes!
True
PCA
PCA
Analyzing The Signals – Pattern
Recognition
Questionnaire
PCA
PCA
Do you think you need a
diet?
Nope
False
PCA
PCA
Analyzing The Signals – Pattern
Recognition
Results
PCA
PCA
correlated signals
PCA
non-correlated signals
PCA
Analyzing The Signals – Pattern
Recognition
The first order vector is not expected to
give us much information, but we
hope the second or the third order will
help us to distinguish between lie and
truth.
The PCA algorithm was executed 4 times
– True left, True right, False left and
False right.
Analyzing The Signals – Pattern
Recognition
S - TR
Order 1-TR
S - TL
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Order 1-TL
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Order 1-FL
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Order 3-TR
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Order 3-FL
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Analyzing The Signals – Pattern
Recognition
Order 2-TR
Order 2-TR
Order 2-TL
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Order 2-FR
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Order 2-FL
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Order 2-TL
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Order 2-TR
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Order 2-TL
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Second order
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Order 2-FR
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Order 2-FL
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Analyzing The Signals –
Conclusions
As we can see, the second order of the
PCA can identify lies:
in truth, the signals are corresponding
to each other while in lie, the signal
oppose each other.
THE END