Computers started to be able to recognize human faces in images decades ago, but now artificial intelligence systems are rivaling people's ability to classify objects in photos and videos.

That's sparking increased interest from government agencies and businesses, which are eager to bestow vision skills on all sorts of machines. Among them: self-driving cars, drones, personal robots, in-store cameras and medical scanners that can search for skin cancer. There are also our own phones, some of which can now be unlocked with a glance.

HOW DOES IT WORK?

Algorithms designed to detect facial feature...