Paul Ekman, professor emeritus of psychology at the University of California at San Francisco, explains Screening Passengers by Observational Techniques, or SPOT, a form of behavioral observation that could help secure U.S. airlines.
The man in the cheap brown jacket stood slumped in line, staring at the ground. His hands were fidgety, reaching repeatedly into his inside jacket pocket, or patting it from the outside. A momentary look of anguish, just 1/15th of a second or so, occasionally flashed across his face -- the inner corners of his eyebrows would go up, so that his brows sloped down from the center of his forehead, his cheeks would rise, and the corners of his lips would pull down slightly. He was exhibiting what I call a micro-expression, a sign of an emotion being concealed.
The question was: What was he concealing? And why?