Narrator: This is Science Today. In the last year, national intelligence agencies have become more interested in the research of Dr. Paul Ekman, a psychologist at the University of California, San Francisco, who has been analyzing facial expressions for over four decades.
Ekman: I first became interested in looking at expression and gesture when I was a graduate student and I first started to observe behind a one-way mirror, group therapy sessions and I thought that so much of what was going on wasn't in the words alone, but it was in the expression and the gestures.
Narrator: Since then, Ekman has identified 19 different smiles and analyzed thousands of facial expressions with a measurement system he created. His work uncovering the true feelings behind otherwise deceptive gestures is now being sought by agencies investigating terrorism.
Ekman: It takes us about 12 hours to teach people and give them enough practice so that they can actually use it in their day-to-day work.
Science Today, I'm Larissa Branin.