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Computer Program Detects Deceit
Checks Facial Features for Fake Smiles and Other Clues

Sept. 17, 1999

By Hans H. Chen

APB Video Center

Click photo to see Jeffrey Cohn's high-gradient analysis of surprise.
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NEW YORK ( -- When Susan Smith went in front of television cameras in the fall of 1994 to plead for the lives of her kidnapped sons, Jeffrey Cohn could tell she was lying.

Even before a court convicted her of murdering her boys by drowning them in a South Carolina lake, Cohn, a psychology professor at the University of Pittsburgh, knew Smith was hiding something. He could tell by reading her face.

Now, Cohn and a group of scientists from California say they have created two similar computer programs that can read faces automatically and help investigators tell if someone is trying to fool them.

Cohn published his results in the January issue of the scientific journal Psychophysiology. The results of the California scientists appear in Psychophysiology's April issue.

Measures the motions of emotion

The computer program does not detect specific lies, but it does discern when someone is trying to hide an emotion. Cohn says it analyzes people's faces using electronic markers to measure movement and uses the measurements to tell if a person's expressions -- and the emotions behind them -- are genuine.

At the heart of the computer programs lies the Facial Action Coding System, a 20-year-old system of analyzing facial expressions. Because a genuine facial expression involves so many muscles, people trying to pose often overlook essential elements of a facial expression. The Facial Action Coding System trains observers to pick up on these clues.

For example, when forcing a smile, people frequently forget to lift their cheeks and narrow their eyes. And while someone trying to hide fear can usually suppress a frown, he usually forgets to control his eyebrows. This movement can give him away.

Susan Smith lied to the press and her husband, David, about her children.
Susan Smith lied to the press and her husband, David, about her children.
"People get it wrong, and there are particular places where people tend to get it wrong," said Marian Stewart Bartlett, a researcher with the University of California at San Diego who helped develop the face-reading software. "People might not be as successful in controlling their faces as much as they think they are."

Micro-expressions betray emotions

The scientists say the computer program also simplifies the search for "micro-expressions," flashes of true emotion that pass too quickly for the naked eye to see.

Looking for micro-expressions in a minute of taped interview might take a human investigator an hour, but the new computer programs can analyze a minute of tape in five minutes, Bartlett said.

Despite their hopes for the programs' usefulness, the scientists who developed the face-reading programs said they can only tell when a person is hiding an emotion; they cannot detect an outright lie. But the developers of the system said it could be used alongside polygraph machines to increase their reliability.

Polygraph machines measure changes in a person's body related to the stress of telling a lie, but cannot tell what the lie is. The Facial Action Coding System can look for hidden facial expressions that reveal what a person is really feeling when he is telling that lie.

"There are a number of things people do when they are attempting to hold back or deceive that good polygraph examiners are sensitive to but have no way of quantifying," Cohn said. "The kind of approach we're working on provides a way to quantify this information that will make it useable."

Hiding emotions, or trying not to sneeze?

The Automated Face Analysis Program uses 'Perspective Alignment' to account for rigid head movements.
Some critics remain skeptical of the face readers' potential.

"Who will be the first person whose credibility is ruined because they're on the edge of a sneeze?" said Doug Williams, a former polygraph operator for the Oklahoma City Police Department. Since retiring, Williams has found a second career debunking polygraph machines and other "lie-detector" devices.

"I've run about 6,000 polygraph exams," he said. "I've never seen anybody yet who had a discernable lying expression on their face."

Even current polygraph operators doubted the face readers' usefulness. Don Weinstein, the president of American Polygraph Association, said polygraph machines measure involuntary responses to lying.

Facial muscles, which a person can control at will, are just too unreliable to be used as proof of a crime.

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"I'd have to see what this thing would look like," Weinstein said. "It absolutely astounds me. I would invite somebody to demonstrate it to me."

Not ready for prime time

According to both Cohn and Bartlett, a computerized Facial Action Coding System is still several years away from commercial use. And while the system has not yet made its way into the interrogation room, both scientists said police officers could be using automated facial analysis in less than five years.

"We're developing this as a tool for use in research and in a range of applied settings, and forensic applications would be one," Cohn said. "I would see the face expression analysis as an important adjunct to the traditional polygraph examination."

Hans H. Chen is an staff writer (

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