Human Lie Detector

We're notoriously bad at determining when someone's pulling the wool over our eyes; studies show we get fooled half of the time. We could stand to learn from receptive aphasics, people who cannot understand speech—and have the strange ability to ferret out liars from truth-tellers based on facial expression alone.

Researchers from Massachusetts General Hospital and the University of California at San Francisco showed two videos to a group of subjects. In the first tape, a woman described pleasant images she saw on a TV screen. In the second, the woman viewed disturbing images and lied in her description of what she saw. The participants included stroke victims who had suffered damage to the left hemispheres of their brains—the region linked with speech recognition—and who could understand spoken words, but not full sentences. Though they had no idea what the woman was saying, these subjects were far better than others at judging whether she was being honest, detecting lies 73 percent of the time. Other subjects did so only about 50 percent of the time.

"Aphasics pay attention to fleeting facial expressions," explains study author Nancy Etcoff, Ph.D., a psychologist at Massachusetts General. "Their ability to spot liars seems to be an acquired skill." So the rest of us should focus on people's body language—not the lines they feed us—if we want the real truth.

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