A researcher at Massachusetts Institute of Technology recently developed software that can identity someone from his or her facial characteristics and even determine that person's mood. The "facebase" is already being sought out by the Defense Department and other government agencies and could evolve into an effective and potentially worrisome tool for police surveillance.

Last year, Lau won contracts to provide imaging systems to the Registry of Motor Vehicles and the Department of Transitional Assistance. The technology would allow the Registry to quickly sift through its facebase to determine if a driver's license applicant is already registered under different names.

With its set of 100 eigenfaces, the computer can now easily analyze all the faces in its facebase, each of which can be expressed as a combination of the eigenfaces—more of some, less of others. The eigenfaces are like filters that allow the computer to see just one aspect of a face at a time. They are also a sort of shorthand for describing just how each face differs from the average.