There is no single telltale sign of lying, but rather a constellation of possible signs that may "leak" from the liar during the act. We'll discuss both verbal and nonverbal signs of lying in this section.
First, we'll examine some nonverbal signs of lying. One sign that escapes most people is the flashing of a microexpression. Microexpressions are superquick expressions that cross over people's faces against their will and without their awareness. These provide a true look at their honest feelings about a matter. While most people aren't looking for such clues, a good many of us detect them without knowing what just happened. The information we glean -- detecting a millisecond-long look of anger in the middle of a smile -- is often chalked up to intuition or a "gut feeling." If your "gut" is telling you something isn't quite right with a person, you very well may have detected a microexpression on that person's face that doesn't mesh with what he or she is saying.
Another nonverbal sign of lying is a forced smile, which generally involves only the muscles of the mouth and not the rest of the face. A sign of deception is a smile or other gesture -- such as nodding "yes" during a denial -- that contradicts what is being said. When we normally interact, both speech and body language happen naturally, without specific thought. When we lie, however, not only must we appraise the truth, construct a plausible lie and then verbalize it, we must also decide which body gestures best match the lie, or rather best represent the telling of the truth. All of this thought leads to mis-matching words and body language.
Someone who's lying may feel attacked and get in a defensive position. He or she might turn away from the questioner, cross his or her arms or even move farther away. Liars may noticeably fidget, especially during a pause in the conversation.
There are other nonverbal cues that many people think are surefire signs of lying but aren't, such as increased blinking, scratching the face or nose, or placing a hand over the mouth while speaking. These signs are only good indicators when they represent a change in the person's normal behavior (that is, the behavior immediately preceding the suspected lie). Maybe the guy who's blinking a lot has an eyelash in his eye, and the girl covering her mouth is just self-conscious; however, if the person doesn't blink often during the first three statements and blinks like crazy and scratches his or her neck while giving the fourth statement, then that statement warrants closer examination.
Someone telling a lie will also leak verbal clues that point to dishonesty. Since he or she has to invent an answer, a lie-teller will often spend more time searching for the right word in the course of telling a story. The person might take too long to provide an answer or get words mixed up. To get extra time to think, a liar won't use contractions (opting for "cannot" instead of "can't") and may also repeat questions ("Where was I last night?" or "You want to know what I was doing yesterday?").
Since they have to create an alternate reality apart from the truth, liars have difficulty knowing how much of the new story to tell and will often include unnecessary details.
Next, we'll learn what to do if the glove fits.