The answer? Everything.
I admit it: I am completely addicted to Lie to Me. Watch just one show, and I swear you'll be scanning your dates, coworkers and neighbors for flashes of twitchy eyebrows, erratic blinks and one-shouldered shrugs.
Tim Roth stars as Dr. Cal Lightman -- the world's leading expert on deception. Dr, Lightman and his team study facial expressions and involuntary body language to discern when someone is lying, and why.
The show is based on the real-life scientific discoveries of Dr. Paul Ekman, Professor Emeritus at University of California, San Francisco and renowned expert in lie detection. How does he spot the lies? Our faces leak split-second expressions that reveal our true feelings.
According to Dr. Ekman, "A microexpression is a facial expression, usually about a 25th of a second, that is always a concealed emotion." A recent article in Popular Mechanics stated, "Ekman's research indicates that our facial expressions are innate, universal, and nearly impossible to conceal."
Ekman tells me, "Sometimes it's an emotion they know they're feeling and are deliberately trying to hide -- it could be embarrassment or something more sinister."
When Ekman first met his current wife he had been married before. He debated whether or not to tell her about his past. "If she'd seen my microexpression, she would have seen concealed signs of fear on my face."
Was he concealing his past with intent to harm her? No, it was fear that his future wife might reject him "in the first five minutes."
Ekman opted to be honest and tell her about his past right away. Turns out it was a good decision, they've been happily married for 30 years.
Try as we might, we can't fully conceal our guilt, shame, anger, happiness, disgust, fear, or other emotions. But what microexpressions don't reveal is why someone is having those feelings. "No emotion tells you its source," says Ekman.
And if you can't conceal a microexpression, neither can you fake one, he adds.
That's right, everything you need to know about your date is written all over his or her face. You just have to know where to look.
Or rather, you have to know how to spot those split-second grimaces and figure out whether they mean contempt, anxiety or just a bad cheeseburger.
To the untrained eye, they are virtually impossible to spot, but we can learn to read them, quite quickly apparently -- in about an hour, according to Ekman (such as with this tutorial).
But do you really want to know every single thing your date is feeling?
"Romance is in part an illusion you don't want to destroy," Ekman says and the ability to read microexpressions is a mixed blessing. "Once you learn it, you can't turn it off. You will always recognize concealed emotions. You will be a privacy invader. You'll see things people won't know you're seeing."
Ekman and his research partner Dr. Maureen O'Sullivan, professor at the University of San Francisco (the character of Dr. Gillian Foster, played by Kelli Williams, is based on her) have found that a very small percentage of people (less than one per cent) are natural-born lie detectors and can detect deceit without any formal training. They refer to these naturals as "Wizards."