New Airport Screening Method Catches More Than 20 Times As Many Liars

Security agents should chat more and watch less, according to a new study.
Airport security
Media credits

 Anne Worner via flickr |

Media rights

Image rights:

Nala Rogers, Contributor

(Inside Science) -- Around the world, airport security teams attempt to identify terrorists by spotting nonverbal cues such as fidgeting or facial expressions that are believed to reveal deception. But according to many researchers, this approach just doesn’t work. In 2013 the Government Accountability Office analyzed the U.S. program known as Screening of Passengers by Observation Techniques, or SPOT, and found no evidence that the technique used in the U.S. is effective. European airports also have programs based on detecting nonverbal cues.

“My observations of the things that were going on at airports was that they were at best useless, and at worst were actually stopping security agents from doing their job,” said Tom Ormerod, a psychologist at the University of Sussex in the U.K. “The U.K. government said, ‘Listen, if you think the current method’s no good, why don’t you try to develop a better one?’”

Ormerod took his government up on the challenge. With Coral Dando, a police-officer-turned-psychologist at the University of Wolverhampton in the U.K., he developed a new screening method called “Controlled Cognitive Engagement.” At major airports in Europe, CCE detected more than 20 times as many mock passengers as an existing method used to screen passengers for long-haul international flights. The mock passengers were given fake documents and cover stories.

What’s the secret of CCE? Get people talking. With the new method, security agents engage passengers in what feels like a casual conversation, provided you’re telling the truth. If you’re lying, the conversation is a series of traps.

The interview starts with open-ended questions, such as “Tell me a little about the family members you may be visiting,” then continues with targeted questions based on prior answers. Agents ask several sets of questions on different topics. The whole process takes about three minutes, the same as the traditional method it was compared against. An algorithm helps agents come up with unique questions for each passenger. Because the questions are different each time, deceitful passengers have no way to fully prepare.

“We set out to develop an interviewing method that would be essentially benign for regular passengers; it would be just like a conversation,” said Ormerod. “But if you were being deceptive, at some point during that interview you would come under challenge where you would think, ‘hang on a second, given what I’ve just said, and given the question they’ve just asked me, I ought to know the answer to this. And they know I ought to know the answer.’”

If agents notice that interviewees become evasive and uninformative, they flag passengers to bump them up to a more intensive level of screening.

The researchers compared CCE to a method currently being used to screen passengers for certain long-haul international flights. With the existing method, security personnel ask a series of rote questions and watch for nonverbal cues of deception. This procedure is one of many security screening steps that passengers must go through before getting on an airplane.

At each airport in the study, which were all in Europe, the researchers trained a group of security agents to use CCE. All but two of the 79 trainees passed a two-week training course, and then they began screening all their passengers using CCE. Other agents in the same airport continued to use the older method.

Unbeknownst to the security agents, the researchers sent 204 mock passengers through security. To increase motivation, the researchers paid the mock passengers twice as much if they made it through security without being caught. These individuals were considered “caught” if agents flagged them for further security screening.

Agents who used CCE caught 66 percent of mock passengers. Those who used the traditional method flagged three percent for further scrutiny. Also, it seems unlikely that practice improves a liar's deception. The mock passengers who were given the chance to pass security multiple times were repeatedly caught by agents using CCE.

To ensure that the CCE interviews were not too demanding for genuine passengers, the researchers asked some people about their impressions of the experience after screening. This part of the experiment is unpublished, but Dando said that passengers did not find CCE any more stressful or unpleasant than the traditional method. The study was published online November 3 in the Journal of Experimental Psychology: General.

CCE's use can extend beyond airport surveillance, to areas such as job interviews or law enforcement interrogations, according to Ormerod. The technique could even help doctors evaluate what they are told by patients who may be forgetful, frightened or confused.

Dando believes it’s a myth that behavioral signs such as facial expressions and body language are reliable indicators of deception. 

“The problem with the myths is that they assume that everybody behaves the same way when they’re being deceptive, and they don’t," said Dando.

Judee Burgoon, director of human communication research at the University of Arizona in Tucson, agrees that unpredictable questions are a powerful way of detecting liars, but she is not ready to dismiss nonverbal cues. Burgoon is developing automated devices to detect cues such as eye movements that are too subtle for humans to spot, and she suspects CCE would work even better in combination with such tools. While the CCE approach shows promise, she said, “Nothing should be implemented without more validation.”

Tim Levine, a communication professor who studies deception at Korea University in Seoul, advised a swifter rollout.

“If you take the results at face value, they’re jaw-dropping,” said Levine. He would like to see more details about the technique, and he questioned whether the interviews were as simple for honest passengers as the researchers believe. However, he pointed out that as long as the new method doesn’t increase the rate at which honest passengers are mistakenly flagged, it won’t do any harm. Because the results are so promising, Levine believes airports should start using CCE right away, and continue to track how the method performs. 

At two major airports in Europe, that’s exactly what’s happening. The security agents at these airports who were trained in CCE are continuing to screen passengers using the new method, and, according to the researchers, the agents have enjoyed the new technique.

“It changed their lives from being a series of rote questions, to actually talking to customers and using their minds,” said Dando.

Nala Rogers is a science writer based in Santa Cruz, California. She tweets at @Nala_Rogers.