How does a lie detector (polygraph) work?

Can a polygraph really tell if someone is lying?

You hear about lie detectors all the time in police investigations, and sometimes a person applying for a job will have to undergo a polygraph test (for example, certain government jobs with the FBI or CIA require polygraph tests). The goal of a lie detector is to see if the person is telling the truth or lying when answering certain questions.

When a person takes a polygraph test, four to six sensors are attached to him. A polygraph is a machine in which the multiple ("poly") signals from the sensors are recorded on a single strip of moving paper ("graph"). The sensors usually record:

The person's breathing rate The person's pulse

The person's blood pressure

The person's perspiration

Sometimes a polygraph will also record things like arm and leg movement.

When the polygraph test starts, the questioner asks three or four simple questions to establish the norms for the person's signals. Then the real questions being tested by the polygraph are asked. Throughout questioning, all of the person's signals are recorded on the moving paper.

Both during and after the test, a polygraph examiner can look at the graphs and can see whether the vital signs changed significantly on any of the questions. In general, a significant change

(such as a faster heart rate, higher blood pressure, increased perspiration) indicates that the person is lying.

When a well-trained examiner uses a polygraph, he or she can detect lying with high accuracy. However, because the examiner's interpretation is subjective and because different people react differently to lying, a polygraph test is not perfect and can be fooled.

Brain mapping

Brain mapping is a set of neuroscience techniques predicated on the mapping of quantities or properties onto spatial representations of the brain resulting in maps.

How Brain Mapping Works

Brain Image Gallery

Neurons in the human brain as they transfer information among each other. Want a map of this? It could take a while. See more brain pictures.

The human brain is a knot of 100 billion neurons and support cells. We can store a lifetime of memories there. We can use it to write sonnets and build airplanes. Sure, an elephant's brain is larger, weighs more, and has more neurons, but elephants also lack our abilities. Intrigued? Scientists sure are. That's one reason why they are mapping the human brain, a substantial project that could take decades to complete.

Brain mapping attempts to relate the brain's structure to its function, or finding what parts give us certain abilities. For example, what aspect of our brain allows us to be creative or logical? This is called localization of function.

In mapping brain functions, scientists use imaging to watch the brain working on various tasks. Charles Wilson, a neurobiologist at the University of Texas at San Antonio, explains localization of function this way:

There's part of the brain that has to do primarily with vision and other parts that have to do primarily with sound. Now, can we look in the vision section and say, Is there a special part of the brain that detects red objects and another that detects green objects? Or does the same area detect objects of both colors?

Brain mapping also looks from the outside in. It examines how our environment changes our brain's structure by studying, for instance, how the brain changes physically through the learning and aging processes. Brain mapping also examines what goes wrong physically in the brain during mental illnesses and other brain diseases.

Finally, brain mapping aims to give us a thorough picture of our brain's structure. Google Earth shows us satellite images of our planet and zooms in to continents, countries, states, cities, highways, streets and buildings. A complete structural map of our brain might be similar. It could show us our whole brain; all the regions, functional lobes, specialized centers, thick neuron "bundles" connecting brain parts, neuron circuits, single neurons, junctions between neurons and finally, neuron parts. Scientists are still developing the parts that might form this massive map.

Brain mapping is a collection of many different tools. Researchers must collect images of the brain, turn those images into data, and then use that data to analyze what happens in the brain as it develops.

Read on to learn how researchers map the brain

What Does Human Brain Mapping Actually Tell Us?Google “brain” right now and you’ll find a mountain of news stories on a development known as the BigBrain project, which came out just yesterday: Researchers in Europe and Canada have just mapped the human brain with a precision that’s so strikingly detailed, that it’s unprecedented in humans – and it’s in 3D. The team has devised a way to cut the brain into 20 micrometer-thick sections – far slimmer than the chunky 1 mm sections that have been available with magnetic resonance – dye them, scan them, and reconstruct the slices into a 3D “atlas” of the human brain. But while the research is impressive by any count, and it will certainly gives us some clues into brain cell function and anatomy, there’s a limit to what it can tell us.

To accomplish the mission, the team used the donated brain of a 65-year old woman. It was preserved in formalin and then set in paraffin before slicing. The sections were mounted on glass slides and stained. Then came the scanning prep.

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“After this we had over 7400 histological sections,” says author Katrin Amunts. “And a large number of wooden boxes in the lab to hold them!” She and her team used a flatbed scanner to scan the slices – a process, says Amunts, that took about 1,000 hours alone. Part of the process was the removal of all the artifacts of slicing – folds, ruptures, and other miscellaneous blips.

The 3D image of the brain was formed by reconstructing the slices, making what is essentially a cell-by-cell computer image or “atlas” of the brain. The data take up a mind-boggling terabyte of space.

So what information does brain mapping actually offer? It will certainly give us a better idea of where one region ends and the next begins, for a closer understanding of behavior-brain correspondence. It will also allow researchers to start making simulations, perhaps making it possible to “see” what happens in various disease states, say, in an Alzheimer’s- or Parkinson’s afflicted brain over time. “Researchers can take these images,” says Amunts, “and measure surfaces, thicknesses of cortical layers. It provides precise anatomical measures, and lets us make comparisons to in vivo imaging.”

She adds that this brain essentially becomes a new gold standard in the field. “We have a new reference brain,” says Amunts. “It can help us address questions and data coming from neuroscience about things like receptor distribution, microanatomy. Before this, the data were so scattered, we haven’t been able to compare it very effectively.” Plus, the resolution from MRI scans is much poorer – a clumsy 1-mm thickness, which is “not good enough to address questions about microstructure,” adds Amunts.

In terms of the person-to-person brain differences that are inevitable, Amunts says, “This is true. And we’ve actually started second brain, to account for some of these. We’re aware of intersubject variability. But the first brain has all the areas that you need.” She says her team probably won’t do more than a few brains in total, given the massive time commitment each requires.

And BigBrain will almost certainly have some major clinical implications, giving doctors a hand in neurosurgery and in placing electrodes during procedures like deep brain stimulation (DBS).

What the project doesn’t do is tell us a whole lot about anything else – those “deeper” questions that we’re all dying understand. In this way, the headlines touting BigBrain’s ability to work such magic as to “unlock the secrets of the mind” and that kind of thing may not to so accurate.

In fact, in a well-timed New York Times editorial this week, David Brooks makes the important point that the brain is not, after all, the mind, and as much as we’d like to think we’re getting closer to grasping human consciousness and thought with imaging studies, we’re just not. The “neurocentrism,” he says, that we’re so attached to is actually not serving us so well at all. In his words, “An important task these days is to harvest the exciting gains made by science and data while understanding the limits of science and data. The next time somebody tells you what a brain scan says, be a little skeptical. The brain is not the mind.”

When asked about the limits of the 3D brain atlas, Amunts says that though it doesn’t answer all questions, ultimately, basic neuroscience is critical for what it can offer us. “I’m a physician by training. I want to know why the region in the language area is involved in language. You have to understand brain first.” Her past work has mapped out the architecture of the brain, and, she says, the specificity can be dazzling. “And now we can look at everything in the same brain. If you only do small bit, you don’t have the full truth. But now we can analyze the whole brain.”

So this is on many levels a big accomplishment for Europe’s Human Brain Project, which has the not unlike our own BRAIN initiative. But there are limits to what it can tell us, and it only gives a peek at what’s actually going on in our heads. There’s much more work to be done, and a staggering number of questions that still need answers

What is narco-analysis, polygraph test and brain-mapping?New Delhi, May 5 (IANS)

The Supreme Court on Wednesday said narco-analysis, polygraph and brain-mapping tests cannot be conducted on an accused or a suspect without their consent.

These tests, which are often used as aid during investigations by probe agencies, are different from each other, but are all aimed at collecting vital information.

Narco-analysis is a controlled administration of intravenous hypnotic medications called truth drugs on a suspect to procure vital information.

A polygraph, popularly referred to as a lie detector, is an instrument that measures and records

several physiological indices such as blood pressure, pulse, respiration and breathing rhythms and skin conductivity while a suspect is asked a series of questions. Deceptive answers are said to produce physiological responses that can be differentiated from those associated with non-deceptive answers.

Narco Analysis

A method of psychological investigation in which the conscious or unconscious unwillingness of a subject to express memories or feelings is diminished by the use of a barbiturate drug.

Origin: 1935–40; narco- + analysis

What is a narcoanalysis test? how is it conducted?

The technique of using "drugs" for the purpose of investigations is called as: NARCOANALYSIS TEST and is also known as the "TRUTH SERUM TEST ”. According to Webster’s Dictionary, the word narco analysis had its origin in the 20th century and is coined from ‘narco-’ + ‘analysis’. It means psychoanalysis using drugs to induce a state akin to sleep.

NARCO-ANALYSIS OR TRUTH SERUM TEST,is believed that if a person is administered a drug which suppresses his reasoning power without affecting memory and speech, he can be made to tell the truth. Some drugs have been found to create this ‘twilight state’ in some persons. These drugs are being administered in some countries including India. The term narcoanalysis was introduced in 1936 for the use of narcotics to induce a trance like state wherein the person is subjected to various queries. Under the influence of the drug, the subject talks freely and is purportedly deprived of his self-control and will power to manipulate his answers. The underlying theory is that a person is able to lie by using his imagination. In the narcoanalysis test, the subject’s imagination is neutralized and reasoning faculty affected by making him semi-conscious. The subject is not in a position to speak up on his own but can answer specific and simple questions. In this state it becomes difficult for him to lie and his answers would be restricted to facts he is already aware of. His answers are spontaneous as a semi-conscious person is unable to manipulate his answers.

Automated fingerprint identificationAutomated fingerprint identification is the process of automatically matching one or many unknown fingerprints against a database of known and unknown prints. Automated fingerprint identification systems are primarily used by law enforcement agencies for criminal identification initiatives, the most important of which include identifying a person suspected of committing a crime or linking a suspect to other unsolved crimes.

Automated fingerprint verification is a closely related technique used in applications such as attendance and access control systems. On a technical level, verification systems verify a claimed identity (a user might claim to be John by presenting his PIN or ID card and verify his identity using his fingerprint), whereas identification systems determine identity based solely on fingerprints.

With greater frequency in recent years, automated fingerprint identification systems have been used in large scale civil identification projects. The chief purpose of a civil fingerprint identifications system is to prevent multiple enrollments in an electoral, welfare, driver licensing, or similar system. Another benefit of a civil fingerprint identifications system is its use in background checks for job applicants for highly sensitive posts and educational personnel who have close contact with children.