Liar Liar Pants on Fire

So investigators must concoct intricately staged simulations and acknowledge that accurately measuring the effectiveness of new lie detection technologies is extremely difficult-in some sense, it's a quixotic quest. "Lying is probably one of the most complicated things that we do," says Jennifer Vendemia, a psychology professor at the University of South Carolina.


Still, some of these new approaches are intriguing because they look directly into the brain, seeking out lies at the moment in which they are formed, rather than merely measuring, as the polygraph does, the secondary signs of nervousness such as sweating and a racing heart. That shift represents a potentially huge leap forward, according to Stephen Kosslyn, a psychology professor at Harvard University. "Current lie detection tools," he says, "are at least one step removed from the organ that's actually doing the lying."


These emerging brain-based technologies offer researchers a window into the mind, revealing basic truths about the nature of deception. For one thing, investigators are learning that lies may originate in different parts of the brain-simple denials are formed in one area, elaborate confabulations in another. Moreover, the new experiments offer physical evidence of something that philosophers have long suspected: It takes more mental energy to lie than to tell the truth.


The most advanced equipment being harnessed to measure deception is the functional magnetic resonance imaging (fMRI) machine, which uses strong magnetic fields to induce the molecules within brain tissue to emit distinctive radio signals. By mapping those signals onto images of the brain taken in rapid succession, the fMRI monitors the movement of blood-and, from that, can determine which areas of the brain are activated by a particular task.


In a seminal fMRI lie detection study, Daniel Langleben and colleagues at the University of Pennsylvania School of Medicine gave volunteers a playing card and a handheld yes/no clicker. The subjects were told to lie when shown a question that would reveal their card, but to answer other queries honestly (see illustration on the opposite page). When these people gave truthful answers, the fMRI showed increased activity in parts of the brain related to vision and finger movement. When they lied, the same areas lit up-but so did areas in the front part of the brain that have been shown to regulate decision making in the presence of rival information. "They activate when you make a choice unconsciously," Langleben says. Which means, he adds, that lying apparently takes more mental effort than telling the truth. "Truth is the baseline," he says. "St. Augustine was right when he defined deception as intentional denial of truth. If you don't know the truth, you can't lie."