polygraph

Everyday

1. A polygraph is a machine that measures a person's breathing, heartbeat, blood pressure and sweating while they answer questions; it is often called a «lie detector». tree →
2. A polygraph test is the questioning done with this machine. tree →

In the lessons

In stories and TV shows the polygraph is used to try to catch liars. In lessons about truth and lies we learn that it measures nervousness, not lies themselves, so it can make mistakes. Phrases: «take a polygraph test», «pass the polygraph», «lie detector».

Examples

• The detective asked the suspect to take a polygraph test. tree →
• A polygraph measures how fast your heart beats. tree →
• He was so nervous that the polygraph showed he was lying, but he was telling the truth. tree →
• Scientists say polygraphs are not always right. tree →
• In the film the spy fooled the polygraph. tree →
• The polygraph has wires that go on your fingers and chest. tree →

Note

Countable: polygraph, polygraphs. Myth: a polygraph cannot read your mind or truly «detect lies»; it only shows body signs of stress, which honest nervous people can also have. Many courts do not accept polygraph results.