"Generally, people don't want to admit they've lied," said Catalina Toma, communication science professor at the University of Wisconsin-Madison.
"But we don't have to rely on the liars to tell us about their lies. We can read their handiwork."
Using personal descriptions written for Internet dating profiles, Toma and Jeffrey Hancock, communication professor at Cornell University, have identified clues as to whether the author was being deceptive.
The researchers compared the actual height, weight and age of 78 online daters to their profile information and photos on four matchmaking websites. A linguistic analysis of the group's written self-descriptions revealed patterns in the liars' writing.
The more deceptive a dater's profile, the less likely they were to use the first-person pronoun "I."
"Liars do this because they want to distance themselves from their deceptive statements," Toma said.
The liars often employed negation, a flip of the language that would restate "happy" as "not sad" or "exciting" as "not boring." And the fabricators tended to write shorter self-descriptions in their profiles - a hedge, Toma expects, against weaving a more tangled web of deception.
"They don't want to say too much," Toma said.
"Liars experience a lot of cognitive load. They have a lot to think about. They less they write, the fewer untrue things they may have to remember and support later."
Liars were also careful to skirt their own deception. Daters who had lied about their age, height or weight or had included a photo the researchers found to be less than representative of reality, were likely to avoid discussing their appearance in their written descriptions, choosing instead to talk about work or life achievements.
The toolkit of language clues gave the researchers a distinct advantage when they re-examined their pool of 78 online daters.
"The more deceptive the self-description, the fewer times you see 'I,' the more negation, the fewer words total - using those indicators, we were able to correctly identify the liars about 65 percent of the time," Toma said.
A success rate of nearly two-thirds is a commanding lead over the untrained eye. In a second leg of their study, Toma and Hancock asked volunteers to judge the daters' trustworthiness based solely on the written self-descriptions posted on their online profiles.
"We asked them to tell us how trustworthy the person who wrote each profile was. And, as we expected, people are just bad at this," Toma said.
"They might as well have flipped a coin ... They're looking at the wrong things," Toma added.
About 80 percent of the 78 profiles in the study strayed from the truth on some level.
Weight was the most frequent transgression, with women off by an average of 8.5 pounds and men missing by 1.5 pounds on average. Half lied about their height, and nearly 20 percent changed their age.
Studying lying through online communication such as dating profiles opens a door on a medium in which the liar has more room to manoeuvre.
The study has been published in the Journal of Communication.