2006-09-19 20:53:24 · 19 answers · asked by Anonymous in Science & Mathematics ➔ Other - Science
by cheking the resistence in the body ... our body resistence will vary as we lie
2006-09-19 21:00:05 · answer #1 · answered by achu 2 · 0⤊ 0⤋
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.
2006-09-21 03:42:20 · answer #2 · answered by Sandy 1 · 0⤊ 0⤋
Well, in most parts of the world it is considered that lie detectors do not actually work, or at least not with sufficient reliability to be practically useful.
Lie detectors work on the assumption that lying induces stress (which it may or may not) and that stress induces detectable physiological changes (which it may or may not).
Different lie detectors use different techniques to measure this stress. The most common is to measure skin resistance, on the basis that we sweat when under stress (so reducing skin resistance). Others measure heart rate or even the effects of stress on the voice.
More reent research has measured brain waves directly to look for tell tale signs of lying.
2006-09-20 04:00:21 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Various sensors attached to your body pick up your, heart rate, breathing rate, and level of sweat on your skin. Generally speaking if these things get quicker it denotes a lie, this assumption is somewhat reliable but is by no means 100% accurate.
2006-09-20 03:59:35 · answer #4 · answered by LenV 2 · 1⤊ 0⤋
In a Polygraph test, there are 3 different types of tests which are conducted..
1) Brain Mapping
2) Narco Analysis
3) Truth Serum
In Brain Mapping test, various probes are attatched to the body of the accused. and he is asked questions and his reactions are monitored on screen.. reactions as in heart beat, blood pressure, perspiration etc..
In Narco Analysis, a set of questions is asked.. first he is asked normal questions,ex,whether his name is this and whether he resides at this place.. his reactions are monitored..
then he is asked questions related to the case and then his change in reactions are again monitored..
In Truth Serum he is given some solution to drink and then he is again asked questions pertainig to the case..he tends to answer it correctly because of the effect of the solution..
so, basically these tests are conducted to extact the truth 4m the accused by way of tracking the difrence in reactions when he is asked general questons and when he is asked questions as of the case..
2006-09-22 01:22:15 · answer #5 · answered by generation next 1 · 0⤊ 0⤋
It measures a number of things. Heart rate, skin moisture, and other body changes. These changes can indicate a person is lying. Polygraphs are not 100 percent reliable and many people are able to beat them.
2006-09-20 04:01:54 · answer #6 · answered by Warren D 7 · 0⤊ 0⤋
durin a lie detection test,d person's heartbeat n pulses r monitored through diff devices.wen a person is speakin d truth his\her heartbeat and pulse remains normal but wen some1 is lyin ,dere is a deflection in d pulse and heartbeat graph.dis is how d detector wortks. ;)
2006-09-20 04:10:55 · answer #7 · answered by Sanchita 1 · 0⤊ 0⤋
The lie detecter identifies the person is lying or not by their increased pulse rates
2006-09-21 11:25:59 · answer #8 · answered by ARAR 1 · 0⤊ 0⤋
It checks for variations in blood pressure, pulse rate etc. So if you lie your BP and pulse rate shoot up.
Structured questions are asked to bring about these variations and are beleived to be 95% accurate
2006-09-21 03:46:34 · answer #9 · answered by Mahesh S 1 · 0⤊ 0⤋
it detects your pulse and breathing(that's why you see in the movies that belt around the chest). first they ask standard questions like : what's your name or do you have a son(they all ready know the answers..... this is used to calibrate the device,machine....) and then if get nervous at some Q's then you might be a liar
2006-09-20 04:07:24 · answer #10 · answered by sonycwat 1 · 0⤊ 0⤋
According to the method of narco-analysis, lie detection is found. But the method is not yet proved to be cent per cent correct.
2006-09-21 05:06:40 · answer #11 · answered by SRIRANGAM G 4 · 0⤊ 0⤋