Looks familiar?

摘要

Smile―you're on CCTV. But you'd better not grin if you're trying to go undetected. It turns out that face-recognition systems have a much better chance of matching a suspect to an image if the pictures in their databases are of smiling faces rather than blank looks. Face-recognition systems are now pretty good at matching a person to a stored image, but only when the database is relatively small, says Yaser Yacoob, who researches computer vision at the University of Maryland. "As you start having thousands and even millions of faces in a database, they are going to look more and more alike," he says. So systems that compare large databases of faces with even larger numbers of faces in a crowd are likely to make lots of mistakes: more mugshots means more false positives.