Porter, who has been studying deceptive behavior for 15 years, has a new study in the current issue of Psychological Science that indicates it is possible for persons involved in law enforcement and airport security, and the rest of us as well, presumably, to learn how to recognize those tell-tale expressions of deceit in someone else, even if we can't control it in ourselves.
His research shows earlier studies that indicated those expressions lasted less than a fifth of a second were incorrect, because in many cases they last nearly a full second long. That should allow a trained eye enough time to detect them, he added.
Porter and graduate student Leanne ten Brinke recruited 41 undergraduate students to see whether they could mask their true emotions.
Each participant sat in front of a computer monitor as a series of 17 photos flashed briefly on the screen. The subjects were instructed to show specific expressions, like happiness, as the images appeared.
However, the images actually represented four very different emotions, disgust (a severed hand), happiness (puppies playing), sadness (baby in distress) and fear (open-mouthed rabid dog).
If a subject is supposed to show happiness when the picture of a distressed baby is shown, then clues to that deception should emerge because the emotion of happiness is false.
During the experiment, an untrained observer sat behind the computer where the image was not visible, and rated each participant's performance.
A lack of training, which was intentional, resulted in a predictable finding: You can't tell who's lying unless you've been trained.
"We found they were pretty bad at it," Porter said. In fact, they could have been just as accurate if they had flipped a coin.
But were the people able to falsify their emotions? The answer to that came when the experts viewed footage of the experiment in slow motion.
All of them flunked. Each one showed an involuntary muscular reaction at least once, Porter said.
So for the liar, "there's absolutely no hiding place," Porter added. "You can't monitor your face, like you can your body language, because you can't see it. You can see whether your arms are waving, or your foot is tapping, but you can't see your face, and you can't control it if powerful emotions are going on."
The researchers were able to document those involuntary micro-expressions less than a second long, but that's because ten Brinke spent more than a year carefully analyzing more than 100,000 video frames.
She said lying was most likely to show up when the participant was instructed to show disgust or fear, so those emotions are harder to disguise. Apparently, it's a piece of cake to look happy when we're really sad or disgusted.
"That's probably because we've had so much practice at looking happy," Porter said. "We're able to put on a smiley face," he added, because we've been conditioned to do so.
After all, we all tell those little white lies day in and day out.
Lee Dye is a former science writer for the Los Angeles Times. He now lives in Juneau, Alaska.