But a growing field of professionals—from FBI interrogators to autism therapists—is learning to catch these involuntary "leakages" using a surprising piece of technology: the .

In the span of a heartbeat—literally 1/25th of a second—a flash of anger crosses a witness’s face before settling into a practiced smile. In that same blink, a job candidate’s upper lip tightens in contempt, quickly masked by enthusiasm. You missed both. Almost everyone does.

Originally developed by psychologist Dr. Paul Ekman, whose work inspired the TV series Lie to Me , these digital platforms are transforming how we understand honesty, emotion, and human connection. But can software really teach you to spot a liar? And what happens when the average manager or spouse gains access to the "face-reading" skills once reserved for counterterrorism agents? Before understanding the tool, you must understand the target. Micro expressions are universal, involuntary facial movements that occur when a person is trying to conceal a powerful emotion. They are cross-cultural—a surprised tribesman in Papua New Guinea moves his eyebrows and widens his eyes exactly the same way as a stockbroker in London.

Unlike regular expressions, which last half a second to several seconds, micro expressions flash across the face in less than . The untrained eye simply doesn’t register them.

And that, perhaps, is the most powerful tool of all.

Dr. Ekman’s breakthrough was identifying seven basic micro expressions (anger, fear, sadness, disgust, contempt, surprise, and happiness) and coding the specific muscle movements—via the Facial Action Coding System (FACS)—that create them.