Question

Lie-detection tests measure physiological changes in a person, such as pulse rate, blood pressure, and skin conductivity, while they answer questions. Which device is used to carry out this test?

Hint:

This device records pulse, blood pressure and skin conductivity together.

Answer 1

The device used in lie-detection tests is called a polygraph.

Step 1: What the device does.
A polygraph is an instrument that simultaneously records several physiological signals from a person, including heart rate, blood pressure, breathing rate, and the electrical conductivity of the skin, which changes with sweating.

Step 2: How it works.
The idea behind the polygraph is that telling a lie often causes small, involuntary changes in the body due to stress or anxiety, such as a faster heartbeat or increased sweating. The polygraph traces these signals as continuous lines on a moving chart, or nowadays on a computer screen, while the person is asked a series of questions.

Step 3: Interpretation.
An examiner compares the physiological response during control questions with the response during the actual questions of interest, looking for unusual spikes that might indicate deception.

Step 4: Answer.
So the polygraph is the instrument used for lie-detection tests, working by tracking multiple body signals at once rather than directly detecting a lie itself.