Sometimes, specific phrases and vocal tones can tell you when someone is being deceptive. When a person is accused of lying, their stress response increases and their anxiety goes up. Due to this, the liar will often grow defensive and assert that they are telling the truth to avoid getting caught.

When a truthful person is accused of lying, they will deny it, but then will follow up with information to disprove the other person’s opinion. On the other hand, a liar will deny their fabrication and then become very defensive, using phrases such as, “I would never lie!” or “It’s the truth, I swear!” They further the lie in order to convince you of their innocence and thus protect themselves from detection. People who are sure of their honesty will remain calm as they give evidence to prove their truthfulness, while those who have lied are likely to succumb to the pressure.