Omron envisions the smile software being used in marketing, perhaps to evaluate consumers' reactions to a new product or to an advertising campaign. A smile checker could also help train customer-service staff to meet Japan's legendarily high standards, Seddon says.

"Clearly, it's an interesting thing," says Joseph Atick of L-1 Identity Solutions, based in Stamford, CT, which supplies identification technology, primarily for security applications. "If you can read people better, you can serve them better."

A smile in isolation is easy to detect, but the bigger challenge is to develop systems that can recognize the concerto of facial actions that make up complex expressions like confusion, fear, and disgust. "You can also superimpose any other emotion on top of a smile," says Rana el Kaliouby, a postdoctoral associate at MIT who is developing mind-reading machines. "You can have an angry smile, an interested smile--even a confused smile."

"We'd like to be able to distinguish those," says Jeffrey Cohn, director of the Affect Analysis Group, at the University of Pittsburgh.

Sophisticated facial-expression analysis could help mental-health professionals evaluate their patients and monitor their progress. Cohn is studying facial expressions in depressed patients and in people in physical pain.

El Kaliouby says that facial-expression analysis could help autistic people "who need help with real-time analysis of facial expressions and other social cues."

Facial-expression analysis could also have security applications, although Atick is skeptical that a machine can reliably pick out a terrorist on its own. "That smacks of black magic, voodoo," he says. "Tell me what my intent is standing in front of passport control. Maybe it's a long flight and I'm annoyed, but I don't intend to do harm."