If you travel frequently, then you have probably endured more than one security screening interview at an airport. At passport control, for example, border agents ask a few questions, stare at your passport, check you on electronic databases, and then send you on your way.
The purpose of these interviews, of course, is to catch people who are being deceptive. This is a remarkably difficult job. Thousands of people are streaming through airports every day, and only a very small fraction of them are actually being deceptive in any significant way.
Can those few liars be caught effectively?
This question was explored in a field study by Thomas Ormerod and Coral Dando published in the February, 2015 issue of the Journal of Experimental Psychology: General.
They trained two samples of security agents on different methods of screening for deception.
One method focused on finding suspicious signs that are supposed to distinguish lairs from truth-tellers. This technique, which is typical of what is taught to security screeners, involves a scripted set of questions. As passengers answer these questions, agents look for signs of deception like nervousness or a passenger dressed inappropriately for the trip they are going on.
The other method focused on the security interview itself. This technique uses a lot of open-ended questions designed to get the passengers to talk about themselves. The agent asks questions of general knowledge that someone with that background should know. For example, a passenger who claims to be a student at the University of Texas should know where the Student Union is or how to get to the airport from campus. The technique is designed to give the passenger very little control over the direction of the interview. Deceptive individuals like to control the conversation, so that they can focus on the details that they want to discuss.
After this training, about 200 deceptive passengers were sent through security over an 8-month period. Notice, this means that most passengers that any agent saw were genuine passengers. The deceptive passengers were recruited to participate in the study. They were given payment to be in the study and a significant amount of additional money if they passed through security without being called aside for further screening. So, the deceptive passengers had some incentive to get through security. The ability to detect whether this group was deceptive was compared to the screeners’ likelihood of sending genuine passengers for extra screening whose demographic characteristics matched those of the experimental sample.
A few weeks before participating in the study, the deceptive passengers were given a cover story to learn that was tailored to their age and appearance. The example given in the paper was a male police officer who was told to imagine that he was working as an engineer near his hometown and was traveling to Chicago to take part in a fencing competition. The deceptive passengers were told to do research to add information to their backstory. A subset of the deceptive passengers were also given several opportunities to be deceptive at different times, to see if they could improve in their ability to fool the screeners.
The results were striking. Screeners trained with the interview technique caught about 70% of the deceptive passengers, while those trained with the traditional method of looking for cues detected about 5% of the passengers.
You might thing this reflected that the screeners trained with the interview technique just sent more people for additional questioning than those trained in the traditional way. That was not the case. The agents who learned the interview technique were no more likely to send other passengers for additional screening than those who were trained in the traditional way.
You might also think that the interview technique takes longer. It does not. Agents trained with each technique spent about 3 minutes with each passenger. The big difference was that those trained with the interview technique asked more open-ended questions and gave the passengers more time to speak than those trained in the traditional way.
Finally, those passengers who were given several opportunities to get through screening were caught at about the same rate for each try. This finding suggests that it was not straightforward for passengers to learn to beat the system.
The reason why the system is hard to beat is straightforward. If you claim to be someone very different from who you are, there is a wealth of life experience that you simply don’t have. All of the specific details of life from where you shop to how you drive home to what buildings you pass on your way home are second-nature when you are telling the truth and are absent when you are involved in a large-scale deception. These security interviews allow agents to capitalize on the absence of this knowledge when interviewing passengers.
Finally, this research is a great demonstration of the way that psychological research can be used to solve a practical problem. First, the interview technique itself is drawn from extensive research on deception. Second, the test itself is quite well-constructed, and the researchers do a good job of ruling out a number of alternative explanations for the results.