Lie detection is tricky: Is Richard Nixon, here interviewed by David Frost in 1977, on the level? Research finds that “microexpressions” reveal our basic emotions, whether we like it or not. Credit: Associated Press

In the late 1960s, Paul Ekman--then a young psychology professor at the University of California, San Francisco, School of Medicine and just commencing his life's work--filled a San Francisco Victorian with a library of films showing 40 psychiatric patients' faces as they were interviewed. Ekman, who is now a leading figure in his profession, wanted to know whether he could isolate facial expressions to help diagnose mental disorders. A woman named Mary, who had attempted suicide three times before, smiled and spoke cheerily on her tape. As it happened, she was angling for a weekend pass--so that she could go home and kill herself.

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