Vinod Reddy (09005071)

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15 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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Vinod

Reddy (09005071)

Bhanu

Prakash

(09005050)

Hasan

Kumar (09005065)

by


Introduction


Human Lie Detection


Techniques


Micro
-
Expression based design


Controversy & false
-
positive results




Lie detection
is the practice of attempting to
determine whether someone is
lying
.


Usually this involves
asking
the subject
control questions

where the answers are
known to the examiner and
comparing

them
to questions where the
answers are not
known
.



Lie Detectors(though not
an accurate name
)


In event of crime,


Can be used in interrogating


To find the truthfulness of the evidence.


M
ay
prove useful when


hiring
potential
employees


employee theft


revealing
whether or not your future
spouse/girlfriend truly loves you or is after
your
money


Dealing
with your stock broker, sales rep,
lawyer, ex
-
wife, car dealer, mechanic, scam
artist, etc.


To detect whether a person is lying, it is
important to know what to look for in the
person which shows he is lying.


For this we need to know when a lie fails.


Two reasons.


Failed to adequately prepare a lie.



-

lack of adequate thinking


Interference of emotions


-

lack of control on emotions


Two reasons.


Failed to adequately prepare a lie.



-

lack of adequate thinking


Interference of emotions


-

lack of control on emotions


Lies often fail because of inadequate
preparation


When liar comes up with a lie at the spot


May contradict himself


Being caught off
gaurd

when asked questions
which the liar didn’t anticipate.


Lies also betrayed by signs of emotions


Simplest case is when the liar fabricate
convincingly an emotion which is not felt.


Involves concealing his own emotion.


Two types of failures



1)some sign of emotion is revealed




2)the liar may produce some inadvertently




a deception
cuewhich

shows person is
lying.



How do we usually guess whether the other
person is saying the truth?


Based on the behavior of the person



Eye Patterns


Cadence of Speech


Body Language of a Liar


Emotional Gestures



Human lie detection capabilities are limited.


For example,
a meta
-
analysis
of 253
studies of people distinguishing truths from
lies revealed overall accuracy was just
53
percent

-

not
much better than flipping a
coin.


Build one home easily


A polygraph is an instrument that simultaneously
records changes in physiological processes such as
heartbeat, blood pressure, respiration and electrical
resistance (galvanic skin response or GSR)


The polygraph was invented in 1921 by John
Augustus Larson, a medical student at the University
of California at Berkeley and a police officer of the
Berkeley Police Department in Berkeley, California


The underlying theory of the polygraph is that when
people lie they also get measurably nervous about
lying. The heartbeat increases, blood pressure goes
up, breathing rhythms change, perspiration
increases, etc.






A baseline for these physiological
characteristics is established by asking the
subject questions whose answers the
investigator knows. Deviation from the
baseline for truthfulness is taken as sign of
lying
.





There
are three basic approaches to the
polygraph test :
-


The Control Question Test (CQT)
:
compares
physiological
response to relevant questions about the
crime with the response to questions relating to possible
prior misdeeds


The Directed Lie Test (DLT)
:
detect
lying by comparing
physiological responses when the subject is told to
deliberately lie to responses when they tell the truth


The Guilty Knowledge Test (
GKT)
: compares
physiological responses to multiple
-
choice type
questions about the crime, one choice of which contains
information only the crime investigators and the criminal
would know about




Validity

:
Polygraphy

has little credibility
among scientists. A 1997 survey of 421
psychologists estimated the test's average
accuracy at about 61%, a little better than
chance. Critics also argue that even given
high estimates of the polygraph's accuracy a
significant number of subjects (e.g. 10% given
a 90% accuracy) will appear to be lying, and
would unfairly suffer the consequences of
"failing" the polygraph




Functional magnetic resonance imaging or
functional MRI (fMRI) is an MRI procedure that
measures brain activity by detecting
associated changes in blood flow


Studies using fMRI have shown that it has
potential to be used as a method of lie
detection. While a polygraph detects changes
in activity in the peripheral nervous system,
fMRI has the potential to catch the lie at the
‘source’.



The procedure is similar to MRI but uses the
change in magnetization between oxygen
-
rich and oxygen
-
poor blood as its basic
measure


This measure is frequently corrupted by noise
from various sources and hence statistical
procedures are used to extract the underlying
signal



The resulting brain activation can be
presented graphically by color
-
coding the
strength of activation across the brain or the
specific region
studied


Using
this method, studies have shown that
lies can be distinguished 78% of the time



Electroencephalography (EEG)
is the recording
of electrical activity along the scalp. EEG
measures voltage fluctuations resulting from
ionic current flows within the neurons of the
brain


Brain fingerprinting uses EEG to determine if
an image is familiar to the subject. This could
detect deception indirectly but is not a
technique for lie detecting



Cognitive chronometry, or the measurement
of the time taken to perform mental
operations, can be used to distinguish lying
from truth
-
telling


Brain
-
reading uses fMRI and the multiple
voxels activated in the brain evoked by a
stimulus to determine what the brain has
detected



Truth drugs such as sodium thiopental and
marijuana (historically speaking) are used for
the purposes of obtaining accurate
information from an unwilling subject



Information obtained by publicly disclosed
truth drugs has been shown to be highly
unreliable, with subjects apparently freely
mixing fact and fantasy



Non
-
invasive lie detection using non
-
verbal
behaviour

is performed by the
Silent Talker Lie
Detector


It observes and analyses non
-
verbal
behaviour

in
the form of micro
-
gestures while a subject is
being interviewed


It is grounded in the psychological theory that
non
-
verbal
behaviour

is modified by a number of
influences when a person is being deceptive.
These include arousal (in particular stress),
cognitive load, duping delight, and
behaviour

control




At the University of Texas at Austin, psychology professor James
Pennebaker
, PhD, and his associates have developed computer
software, known as Linguistic Inquiry and Word Count (LIWC),
that analyzes written content and can, with some accuracy,
predict whether someone is lying.
Pennebaker

says deception
appears to carry three primary written markers:


Fewer first
-
person pronouns.

Liars avoid statements of
ownership, distance themselves from their stories and avoid
taking responsibility for their behavior, he says.


More negative emotion words,

such as hate, worthless and sad.
Liars, notes
Pennebaker
, are generally more anxious and
sometimes feel guilty.


Fewer exclusionary words,

such as except, but or nor
--
words
that indicate that writers distinguish what they did from what
they did not do. Liars seem to have a problem with this
complexity, and it shows in their writing.



Need for it ?


Standard polygraph


easily faked


Not counted as evidence in courts



Differences from standard polygraph


Micro
-
gestures


Automated


No physical contact needed


No
trained
psycho
-
physiologist required




An Artificial Neural Network (ANN)



Camera



Feed data to the system


Case to be investigated


Date and time of the crime


Details of the crime


Subject’s social background, medical history and
criminal record (with cooperation of subject
)


Data
is now scanned and checks for certain
vindictive words


e.g. robbed, murder, jail


pattern matching techniques


Higher total number of incriminating words
found, closer the value of
I1

to 1.


I1

= fraction of such words found to total such
words recognized by system.



Also known as relevant
-
irrelevant test.


Relevant questions


real issue of concern to investigation

e.g. asking who did it, about evidence, etc.


Irrelevant
questions


provoke no emotion


Irrelevant questions are typically asked first.


Physiological response of no diagnostic value


Guilty


Stronger reaction to relevant questions


Innocent


React similarly





Convert receiving operator characteristic
(ROC) curve/graph (analog signal) to digital
signal.


Difference of consecutive peaks and lows is
taken and averaged out over total number of
such differences to give
I1i

i.e., input variable
for the
ith

response for the general test.


Comparison question test


Ask about general undesirable acts.


Peak
-
of
-
tension test


Questions are asked in an easily recognized order.


A guilty examinee


Responsiveness increases as correct alternative
approaches in question sequence


Decreases when it has passed


Others


e
.g. probable
-
lie and directed
-
lie comparison tests,
known
-
solution peak
-
of
-
tension test




Convert receiving operator characteristic
(ROC) curve/graph to digital signal.


Difference of
consec
. peaks and lows is
averaged out to give
I2i

i.e., input variable for
the
ith

response in the control test


If there are n physiological parameters,


Then #input Variables = (2n+1)


( n


general test, n


control test and 1

pretest)


Input variables are fed into neural network
(trained beforehand) to generate output.



Fuzzy
vs

crisp neural network


Membership functions
vs

weights


Obtaining the data set


(membership functions of each of the input variables)


# data regions = # cases used for training




Similar to Feed Forward Crisp Neural
Network.


Sigmoid
neuron



# output in neural network = n+1


Today’s lie detectors, responses in the form
of graph.


Fuzzy mathematical expressions must be
brought to deal with such situations.


(n+1) membership functions combine to give
a unique membership function outside neural
network, which in turn must be
defuzzified

to
give final output


Min of all membership functions


benefit of doubt
to the examinee


Mathematically, de
-
fuzzification

of a fuzzy
set is a process of rounding it off from its
location in the unit hypercube to the nearest
vertex.


Put simply

For
our system, we propose the value of λ =
0.5; i.e. for any output greater than 0.5 the
output would be 1, otherwise 0.

In this case,
the case 1 would mean the person is a liar,
while 0 would mean the person is truthful.



Difficult to spot and analyze manually.


Requires high processing powers to capture
and analyze micro
-
gestures.




prepare yourself in advance by thinking about
what confessions they are looking for, that
you can know what things to admit and what
things to deny
.



What did we
discuss?


Lie Detection


Human Methods


Techniques used


Silent Talker Design


Controversy


Though Lie Detectors are not completely
accepted by the scientific community, the day
might not be far away…


Bhattacharjee
,
Anwesha

"An Efficient Lie Detector Using FNN", at the
IEEE 7th Student Conference on Research and Development,
University Putra Malaysia,
2009
.
https://sites.google.com/site/fnnliedetector/


Charting
the
behavioural

state of a person using a
back propagation
neural network, Janet
Rothwell
,
Zuhair

Bandar, James O’Shea, David
McLean. 2009


Simple Lie Detector
-

http://
www.aaroncake.net/circuits/lie.asp


http://sosuave.net/forum/showthread.php?t=166543


Use of Fuzzy Set Classification for Pattern Recognition of Polygraph.
Knapp,
Ulka
,
jacobs
, 1995.