By Dr. Ken Broda-Bahm:
On a recent trip returning to the U.S., I was eyed closely as I answered a series of apparently mundane questions from the uniformed American agent. Where was I born? Where do I live in the U.S.? How long had I been gone? What cities had I visited? And so on. My interviewer may have been a “Behavior Detection Officer,” a role described in a recent article in The New York Times focusing on the program in which the Transportation Security Administration (TSA) invested over $1 billion in order to train screeners to read body language in order to identify potential terrorists. By checking to see who seems stressed, who is blinking too fast, who is averting their eyes or looking up and to the left, the trainers and their government pupils believe that they can improve their odds at spotting liars. But after a review, the Government Accountability Office (GAO) is recommending that the program be cut off, for one simple reason: It doesn’t work. A thorough review of the science, including a review of more than 200 studies (Bond & DePaulo, 2006), the conclusion is that people are notoriously bad lie detectors, and training just seems to serve to increase people’s confidence in their lie-detecting ability, but not their actual performance in it.
Focusing on what are supposed to be the classic “tells” of deception, the ability of human lie detectors tends to hover at about the same level as chance: 47 percent correct in spotting a liar and 61 percent correct in spotting a truth teller. Despite this, the TSA and scores of other law enforcement agencies continue to invest heavily in that training. More than science, that emphasis reflects a folk belief that body language must be important. Based on all the attention we put into it, people are led to think that there must be some kind of definite and reliable meaning in it. But the reality is more complicated. Yes, nonverbal communication matters as part of the message. But, no, it does not carry clearly defined or universal meanings that make it a reliable test of credibility and truthfulness. Both sides of that equation carry some important implications for legal persuaders. For the witness on the stand evaluating the jurors during testimony, it means you cannot really tell what they’re thinking. But for those jurors looking back and evaluating the witness, it means that at least some of them will feel that they can gauge honesty by looking at the witness’s body language. And the legal instructions will even aid and abet that focus by telling jurors to look at “demeanor.” In this post, I’ll take a look at the disconnect between our beliefs on body language and the scientific reality, along with some of the implications for legal communicators.