Turns out people are really good at telling lies…and really bad at detecting them.

Studies show most people are only about 50% accurate in spotting a lie. That’s the same as a coin toss. After years of research on nonverbal communications and deception, University at Buffalo Professor Mark Frank concludes, “There is no Pinocchio response.”

While lie detection technologies surpass human accuracy, achieving absolute reliability remains elusive. That’s why in most states, polygraph tests (with their 15% to 25% error rates) are not admissible in court. The tests are good at recognizing physiological stress signals, but they can’t distinguish between stress shown by people because they feel guilty, and stress shown by people because they feel wrongly accused. One more problem: people who are least likely to show stress when questioned about crimes are psychopaths and sociopaths, who feel no guilt about their actions.

Most of us can detect stress signals from people we know really well, such as our spouses, partners and kids. We have to remind ourselves not to jump to conclusions about what’s motivating the stress.

Think about a time when you thought someone was lying, but it turned out you were wrong. What signals made you think they were lying? What questions did you ask to get to the truth?