How a lie detector test works

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An increasing number of companies in India are offering lie-detector tests to individuals and companies trying to catch out deceitful spouses and cheating employees.

One such company, Helik Advisory, which has been operating for a year, says it is getting more enquiries about its polygraph tests every day.

Using a number of sensors attached to the body, physiological changes can be used to determine whether someone is telling the truth.

A major change in any pattern, also known as a "response conflict", is a sign a person is lying.

Polygraph tester Deepti Puranaik put the BBC's Rajini Vaidyanathan through a lie detector to show her how the technology works.

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