May 19, 2014 7:08 p.m. ET

"How can I tell if someone is lying to me online, or in a text or an email?"

Readers have been asking me about this issue a lot lately. In an age of online dating and constant emails, texts and social media, people write to tell me about communications that feel incomplete, disconnected or just a little off. Their gut is telling them something is wrong.

With so much room for ambiguity and misinterpretation, it's hard to tell what is fact and what is fiction. This can happen when we are flirting with a stranger on an online dating site, as well as when we are messaging with a work manager or planning a family party with a sibling.

Experts say the vast majority of our interpersonal communication involves body language—gestures, facial expressions, tone of voice. Take these intangibles away, as we do with digital messages, and we are left with far fewer clues as to what is really going on.

In the office and elsewhere, many relationships begin on email and remain that way for years. So it's critical to have tools to help evaluate whether the person on the other end of a digital communication might be lying.

Research shows people tend to be suspicious of information they receive online but override their suspicions and trust the information anyway. Experts call this our "truth bias."

We often have powerful emotional reasons to believe what someone is telling us. We really want to believe the message from the cutie on the dating site is real. Ditto the text saying our spouse is working late.

A few years ago, Brian Bohne, of Lauderdale by the Sea, Fla., was contacted through an online dating site by an attractive woman in Russia. Almost immediately, she asked to communicate via email.

From the start, Mr. Bohne had suspicions—her messages appeared to be written with the help of translation software—but he decided to play along.

He says he found her story of longing to get out of her small town believable. He was surprised that she wrote for months, professing her love without asking for money.

"Waking up in the morning to an email love letter can be exciting and flattering," says Mr. Bohne, a 51-year-old retired Army veteran. He found himself thinking, "What if?"

After four months, the woman said she wanted to visit and was going to apply for a passport. Then she contacted him to say if he didn't wire her $1,000, she was going to be in "big trouble." Mr. Bohne googled the email address she had provided—and found it on websites warning about so-called bride scams. He didn't wire the money.

It is possible to catch people lying because they often are bad at it, says Tyler Cohen Wood, an intelligence officer and cyber branch chief at the Defense Intelligence Agency's Science and Technology Directorate, and author of a 2014 book titled "Catching the Catfishers: Disarm the Online Pretenders, Predators and Perpetrators Who Are Out to Ruin Your Life." (Her views on the subject are her own and not those of her employer, she emphasizes.)

"The majority of people prefer to tell the truth," says Ms. Cohen Wood. "That's why when they are lying, the truth is going to leak out."

There will be clues. To identify them, Ms. Cohen Woods suggests using a modified version of a law-enforcement technique known as statement analysis, which is a way to look for deception by analyzing a person's words.

To begin with, pay attention to a person's use of emphatic language. It doesn't necessarily mean he or she is lying, but rather that he or she really wants you to believe what is being said. This is also the case when a person keeps saying the same thing over and over in slightly different ways. "They wouldn't repeat it if it wasn't important to them," Ms. Cohen Wood says.

Look for language that distances the writer from the intended reader. In person, someone may unconsciously distance himself by crossing his arms in front of him. In writing, he can achieve this same effect by omitting personal pronouns and references to himself from a story.

Say he receives a text that says, "Hey I had a great time last night, did you?" He might reply, "Last night was fun."

Another technique to watch out for is the unanswered question. You ask, and the other person hedges or changes the subject. Most likely, the person doesn't like saying no, or doesn't want to hurt your feelings. But he or she also may also be keeping something from you.

"This is all very subtle," says Ms. Cohen Wood. "And it depends on the context." It helps to know a person's baseline behavior—certain words, phrases and punctuation he or she uses often, and the amount of time he or she tends to take when replying. Pay attention when any of this deviates from the norm. Did someone who is usually chatty and full of details suddenly become curt or vague? Did a quiet person turn into a chatter box?

Noncommittal statements are red flags—"pretty sure," "probably," "must have" and, my least favorite, "maybe." ("Did you let the client know, Jim?" "We covered a lot of ground. I must have mentioned it.") "These words leave the person an out," Ms. Cohen Wood says.

Qualifying statements, what I call "tee-ups," are another potential tell. Ms. Cohen Wood says these expressions—"to be honest," "there is nothing to worry about," "I hate to tell you this"—often signal that the person is uncomfortable with his or her next statement.

Another sign of lying is "tense hopping." Someone describing an event that happened in the past usually uses the past tense. But if midway through the story the person starts fabricating, that material plays out in his or her head and leads to a switch to the present tense.

Ms. Cohen Wood advises people who meet someone online to consider a few protective steps. They can apply in other situations, too.

First and foremost, if an email or text exchange feels off, ask the person if he or she would mind switching immediately to phone or Skype. A slightly more skeptical request is to ask for a real-time photo stamped with the time and date.

Ask questions. Pay attention to vague answers, slip-ups and inconsistencies. Don't brush it off if a person tells you he or she is an only child and then mentions a sibling.

One red flag may be a misunderstanding or an honest mistake, Ms. Cohen Wood says. "But if they meet multiple things on the checklist, then you have a problem," she says.

—Write to Elizabeth Bernstein at [email protected] or follow her on Facebook or Twitter at EBernsteinWSJ.