||Psychophysiological Credibility Assessment (PCA), commonly known as polygraph testing, is one of the most misunderstood, misrepresented and much controversial applications of psychology. The two main approaches to PCA are knowledge-based tests and deception-based tests. the techniques, scientific support and criticisms associated with each are discussed. most psychologists appear to be poorly informed about the controversy. Studies show that most commonly used polygraph techniques are highly valid discriminators of deceivers and truth tellers. But many of them criticise it.
WHAT IT IS:
Lie detector or
polygraph as it is technically called is an instrument that monitors the physiological
reaction.It can detect only deceptive behavior of human mapped to lies.
Here the monitoring of the physiological reactions is done. the involuntary change
that occurs in the body when the person is under stress is noted through the instruments.
-ELECTRO DERMAL ACTIVITY
- CHANGE IN BLOOD PRESSURE
are all noted. A polygraph exam has three steps:
This consists of an interview between the examiner and the examinee, where the two individuals get to learn about each other.The examiner sees how the subject responds to questions and
processes information. The examiner designs questions that are specific to the issue
HEART RATE AS A FACTOR IN DETECTION OF DECEPTION:
the subject is under stress, and the rate of heart beat increases from the normal value of 72 beats per min.The Bioelectric signals produced by heart muscle cells. and the Sound produced by the heart. are monitored to detect this change.
Studies conducted show that polygraph is 90% to
98% truthful.the examiners have to to line up the questions and interpret the results properly.