Polygraph aka Lie-detection

1. POLYGRAPH -By Saniya Zedi
Assistant Professor BU

2. WHAT IS POLYGRAPH?
A polygraph, often called a “Lie Detector,” is a machine that measures
human responses to questions, measuring a lot of physiological
symptoms of anxiety or emotion to estimate if the subject is being
truthful or not.

3. INVENTORS
• William Moulton Marston : creator of the systolic blood pressure
test - one component of the modern polygraph.
• John Augustus Larson : first American police officer to use
polygraph in criminal investigations.
• Leonarde Keeler : was the co-inventor of the polygraph.

4. WORKING
Polygraph machine records multiple signals using 4 to 6 sensors
attached to the patient’s body. The sensors usually record:
• The person's breathing rate
• The person's pulse
• The person's blood pressure
• The person's perspiration

6. HOW DOES IT WORK
The Nervous System reacts to different situations differently. For this,
it uses different parts of it, namely :
I. Somatic Nervous System
II. Autonomic Nervous System Arousal- Increased ANS
activity- LIE

7. INSTRUMENTATION
Cardio – Sphygmograph : collects blood pressure and heart
rate data
Pneumograph : measures respiratory patterns
Galvanograph : measures electro-dermal activity or sweat

8. ADMINISTRATION OF TEST
• Familiarizing the subject with the test
• Pre-test Interview
• Formulating Questions
Relevant/ Irrelevant questionnaire
• Analysis of the result

10. ERRORS
Research claims polygraph test has error rates from 15%-40%.
Some individuals are habitual of control breathing, meditation etc can
be a parameter of error in results.
Genuinely scared individual can pose error.
Physical disability and diseased condition.

11. PRACTICE
Q1- Where is Polygraph Required?
Q2- What instruments are used in Polygraph? Mention names.
Q3- Define Forensic Psychology.
Q4- Principle of Polygraph.
Q5- Would you want to be a Forensic Psychologist? Yes/No Support
your answer.