2006-10-12 04:56:29 · 5 answers · asked by sncsrinivasan 1 in Science & Mathematics ➔ Other - Science
From How Things Work:
"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. "
If you search on "lie detector test" you will find other sites -- including hints on how to fool them, though, of course, I am not recommending that! Just to show HOW it may be done.
2006-10-12 05:07:03 · answer #1 · answered by Yahzmin ♥♥ 4ever 7 · 0⤊ 0⤋
It monitors the detectee for symptoms of unease. When smoeone lies they are more likely to be nervous for fear of being caught out. When they tell a lie, their pulse rate will rise, tey will sweat more and their pupils may dilate.
These are some of the things that might be observed during a lie detector test.
This is why the tests can be fooled, because if someone is very confident of their ability to lie then they would be able to fool the machine.
2006-10-12 12:00:08 · answer #2 · answered by Stuart T 3 · 0⤊ 0⤋
what a lie decetor measure isn't so much you say, it measures your heart rate, blood pressure, body temperature, pupil diameter, persipration rate etc... the idea is that these parameters change drastically and predictabley when you are lying as compared to someone telling the truth.
2006-10-12 12:02:41 · answer #3 · answered by Aaronkun 3 · 0⤊ 0⤋
this is all assuming the subject is sane and knows it is a lie.
when my friends in Broadmoor say that God told them to knife their parents, they truly believe it, so nothing would show on the detector.
2006-10-12 12:30:26 · answer #4 · answered by XT rider 7 · 0⤊ 0⤋
it measure you heart, blood and pulse rate while you are ask question.
2006-10-12 12:03:43 · answer #5 · answered by besos 4 · 0⤊ 0⤋