You're on a first date with a woman and you say something HILARIOUS. She laughs! This is clearly going perfectly.
Or IS it? As she's humoring you, you notice her eyes aren't squinting and forming wrinkles. Also, after one chuckle her mouth purses shut into almost a frown. Then, her eyes dart away. The whole thing takes less than a second, but one thing's for sure: you, sir, are going home alone.
Micro expressions -- short bursts of expressiveness on the face -- were first mentioned in a 1966 report by Ernest Haggard and Kenneth Isaacs. They're attributed to seven universal emotions shared by all human beings: anger, contempt, disgust, fear, happiness, sadness, and surprise. And they come about when someone's trying to conceal their true feelings... like that woman sitting across from you on your date, who's trying to be polite but really doesn't think you're funny. Sorry.