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To Find Suspicious Travelers, Try Talking to Them

Brief, directed conversations are more effective at identifying liars than fancy behavioral analysis, experiment suggests.
(Photo: chungking/Shutterstock)

(Photo: chungking/Shutterstock)

By now, it's safe to say that the Transportation Security Administration's behavioral detection officers—agents trained to detect suspicious behavior simply by watching people—aren't very effective. Still, the TSA would like to have tools for detecting potential threats beyond current body scanners, which have their own problems. Now, a pair of English researchers report a new interview approach that could help tell the difference between liars and others.

Lie detection is a controversial subject historically, and a field perhaps dominated more by the hope that it's possible than particularly strong scientific research. Though a few prominent scientists think we can detect lies using physiological measurements or facial expressions, most think that interview techniques are more effective for identifying prevaricators. Interviews, the thinking goes, are more mentally taxing on liars than truth tellers, and they yield more opportunities for liars to contradict themselves. On the other hand, an interview must last long enough to set traps and make them work.

"In contrast to current practice, we propose that security agents should not be trained to identify specific behaviors associated with deception."

Thomas Ormerod and Coral Dando's solution is to engage passengers in brief, friendly conversations that elicit fairly detailed accounts of individuals' travel plans and backgrounds. Those conversations are meant to be quite flexible, so that officers can probe details of a passenger's story as they come up. Key to the approach is to let the traveler do most of the talking, giving agents more information to go on when evaluating a passenger's truthfulness. This contrasts with other methods such as "suspicious signs," which emphasizes a fixed set of questions with generally shorter answers and which often emphasize supposed behavioral tells over information gathering.

To see if their approach worked, the pair went into London Heathrow Airport and a few others and trained 79 officers in their method, called Controlled Cognitive Engagement (CCE). Another 83 trained in the suspicious-signs method also took part. To test the methods, Ormerod and Dando recruited 204 people and gave them one goal: con their way past airport security agents using falsified boarding passes and false identities. The agents' goal was to stop as many of the fakes as they could—a particularly difficult challenge since the fakes had blended in with legitimate air travelers who showed up simply to catch a flight.

The contrast between methods was stark. Agents trained in CCE stopped two-thirds of the mock passengers, compared with a dismal three percent stopped by agents using suspicious signs, which is standard protocol at many airports around the world. Meanwhile, agents using CCE stopped only three percent of real passengers who agreed afterwards to participate in the study—about the same false-positive rate as the suspicious signs method.

"Our results have implications for practitioners, both in security screening, and more generally for professional lie catchers such as police officers and court officials," Ormerod and Dando write in the Journal of Experimental Psychology: General. "In contrast to current practice, we propose that security agents should not be trained to identify specific behaviors associated with deception." Instead, agents should work to draw out potential inconsistencies through conversation, they argue.