PSYC100 term paper-How to detect lie
Instructor: Natasha Ghosh
Our research is based on Lies, their types and old and modern methods of detecting them. First, Lie
is an intentionally false statement, and in order to cheat others or making our own profits. People
often use to lie at various situations like hiding their faults in offices or schools, to cheat someone,
to make easy money etc.
There are rare cases in which lies are justifiable or unintentional. For example, lies made when
someone do not have enough information about that thing or lies made for sake of others. Mostly,
lies create a lot of problem and we need to find to truth in cases like when a truth can save lives of
many people. For example, lies need to be detected. The problem arise that how to know that person
is lying or speaking truth.
How to detect lie? To find the truth, many methods were invented for detecting lies by focusing on
blood pressure or muscle movements etc. In 1895, the first person who used science as a method of
detecting lies was Cesare Lombroso, the Father of Modern Criminology. He used devices called the
plethysmograph and the sphygmograph. The suspicious wore a tight glove, it was attached to a
rubber membrane, and this activated a pen that rolled over the surface of a smoked drum. The speed
of the pen varied with the suspect’s blood flow.
By this result, Cesare believed that, when a person tells a lie, the stress of telling lie affects his or her heart rate and blood pressure. He also developed a machine that measures fluctuations in the
blood pressure for police cases.
Therefore, by this method of observing differences traced by pen, inquirer can catch the lie of the
suspicious. After two years, in 1897, B. Sticker found a new method that could measure suspicious
sweat during the inquiry. After that, in 1900’s, Sir James Mackenzie of Scone, Scotland invented an
early lie detector or polygraph. The machine invented by him can measure the cardiovascular
responses of the patients by taking note of their pulse and blood pressure. Now the polygraph
invented by James questions arises, what is Polygraph?
The polygraph “poly” means “multiple” and “graph” means “to write” is widely used in various
fields like medical and scientific settings for different purposes other than detecting lies. The
polygraph results are based on the changes happening in body’s physiological activity such as
heartbeat and blood pressure. Polygraph is made of various equipments and it measures the changes
in the heartbeat, pulse respiration, changes in brain activity, sweat, muscle changes and skin
conductivity. . (The British Psychological Society, retrieved from
The next question arises, how polygraph test are conducted. Polygraph test are conducted by asking
various questions to the suspicious from simple questions to specific ones. The recording instrument
and questioning techniques are only used during a part of the polygraph examination. It is an
examination, which includes pretest phase, questions was reviewed, and technique is explained
(American psychology association, retrieved from
http://www.apa.org/research/action/polygraph.aspx). The questions were formed on the basis to ensure that the person is able to understand the present
situation or not. For example, most criminal cases investigations were done and in this investigation
person has to pass through simple to questions that are more complex. For example, person is asked
simple questions like “What is your name” or “From where you are”.After this, he or she is asked
some direct questions like did you steal diamond? These questions are direct and they know answer
of the question. These are just to keep check on the person.
Control questions concern misdeeds that are same to those being inquired, but refer to the subject's
past and are usually broad in scope; for example, "Have you ever betrayed anyone who trusted
you?” such questions stimulate the person and this stimulating help us measure changes in the body
and can easily detect if the person is lying.Another example is guilty knowledge test, which is
performed on thieves and are asked many multiple choice question.
The belief behind this test is that if guilty person know the answer he or she will be more stimulated
and will be easy for the investigator to catch the lies. However, there are many controversies related
with polygraph test.Aperson who has not done any crime and if investigation is done on him/her,
the he may feel more arouse because of his fear which can lead to the false decisions.
There are many questions about the accuracy of the polygraph test. The problem with polygraph
testing is that there is no evidence that a physiological reaction is unique to deception.An honest
person can be nervous while answering questions asked by interrogator and a liar may be non-
There is a new method of lie detection which is called “eye tracking”. It tells that whether the
person is lying or not by emphasizing on his or her eye movements. Hatridge and Thompson invent
it in 1948. First, this method also used the head movements of the person and then in 1970’s, the theory of eye tracking was linked to cognitive processes. Using eye movement to detect lies
contrasts with polygraph testing.
The basic difference between polygraph test and eye tracking is found that polygraph test is based
on emotional changes where as eye tracking is besed in cognitive changes.
The main advantage of eye tracking is that the effort to lie or to deceive others during the test can be
seen through the eye movements of the person. In this test, person being interviewed puts a pair of
glasses that are attached to the lie detector. Moreover, another device captures the pictures of retina
with the speed of 60 photos per second.
Then, these pictures are saved in the computer and changes in the retina and pupil is put on the
graph. Interviewed person goes through a series of questions of true and false on the computer
screen. There are some advantages of eye tracking technology over Polygraph.
It is more accurate than polygraph test. It does not another person to interpret the results – the
computer analyzes everything. Thus, the results are very objective. It gives very fast results (approx
in 30 minutes) and it is very cheap. There are some limitations to eye tracking technology. It is only
82.5% accurate. People who are good at lying know how to control their movements when telling a
Psychological disorders can cause problems with data as certain disorders can lead a person to make
a statement they believe to be truth but is actually a fabrication. Current research in the field focuses
on manipulating the psychological and thus measuring the psychological (University of Utah (2010,
July 14). Lie detection: You cannot hide your lying' eyes. ScienceDaily) Using fMRI in Detect Deception
Functional Magnetic Resonance Imaging (fMRI) is a technique that using to detect the blood
oxygenation. The specific brain area that controlling that behavior will be more active than the other
brain areas, when a person doing a specific behavior. In this case, when people were lying, the brain
area that controlling people to create untrue statement will be more activity than the other part of
the brain, and this is why people use fMRI to detect deception.
In 1890, a new view has been published byAngelo Mosso, which is supporting a new developed lie
detect technique in 2013. Mosso said, “The subject to be observed lay on a delicately balanced table
which could tip downwards either at the head or the foot if the weight of either end were increased.
The moment emotional or intellectual activity began in the subject, down went the balance at the
head-end, in consequence of the redistribution of blood in his system…"(James, 1890). He has
created a speculation that is an opposite view in 1800s, when all the scientists in 1800s thought that
a whole brain would not change the blood flow fractionally. In 1948, the basic concept of fMRI
have found by Seymour Kety and Carl Schmidt(2013), which show that neurons are using more
oxygen when they are active; in addition, the blood vessels beside those neurons will expansion and
increase the blood flow in those blood vessels. FMRI is becoming a basically complete technique in
1990s; it is safe and easy for experimenter to analysis the image.
FMIR is used in many different areas such as psychology and medicine.As fMIR is analyzing the
blood oxygenation and blood flow in brain, fMIR is used for detect lies. Human being can not think
without brain; therefore, if we can see how brain is working, then we can know if people were
lying. FMIR is absolutely using to detect deception, and also it is a high accuracy and safe brain
test. However, fMIR has two small limitations, the first one is that people cannot bring any metal
around the machine when it is active, the second one is that it is immoveable, so we cannot use
fMRI to detect deception on street(Meda, 2009). Daniel Langleben is a psychiatrist at the University of Pennsylvania, and James Loughead is a
neuropsychologist at the University of Pennsylvania, there is a research of Langleben and Loughead
shows that there are a few parts of brain will be more active when people are lying. They claim that,
when people are lying, the inferior frontal gyrus and the inferior parietal lobe and bilateral frontal
cortex are those parts that will be more active (Meda, 2009). In this case, when people using the
fMRI to detect deception, they are going to find if those areas are more active than the other areas,
the person who was testee has a high percentage that he/she is lying.
As a technique of detecting lies, fMRI have high accuracy and no damage to human body, which
force it to a new height to be mainstream deception detection. Therefore, the liar in law enforcement
agencies would no longer exist and the judgment in court would be justice.
In modern life, deceptions are around everyone, especially in police office, criminal would try their
best to lie on police officer to escape from charge. Therefore, police need to have something that
can detect whether a person is lying or not; additionally, police need to distinguish a testimony from
a witness is reliable or not. Voice stress analysis would also be a good method when the deception
detects need to be covertly and it can be used over the telephone for banks and insurance companies
(Damphousse, 2008). Nowadays, a great number of law enforcement agencies in United Stated
were using this kind of voice stress analysis machine; however, there are some research shows that
the voice stress analysis machine is not having a high percentage on credibility (Damphousse,
Voice stress analysis software is detecting lies by analyzing the suspect’s voice patterns and tone. It
sounds like that it is a great method to detect lies, but actually it is not really a great method. In a
research by Oklahoma Department of Mental Health and SubstanceAbuse Services, 300 suspects
were arrest by drug using and test the voice stress analysis software. By comparing the data of urine drug test result which is reliable and the voice stress analysis result, fifteen percent of the voice
stress analysis result was wrong presented (Damphousse, 2008).
Why voice stress analysis is less reliable? The answer would be the high number of influence. The
result of voice stress analysis would easily affected by the environment in which would influence
testees’emotion and make them feel stress. People would feel stress involuntarily when they were
in some sp