In Liverpool, England, at a February 2020 conference on the rather unglamorous topic of government purchasing, attendees circulated through exhibitor and vendor displays, lingering at some, bypassing others. They were being closely watched. Around the floor, 24 discreetly positioned cameras tracked each person’s movements and cataloged subtle contractions in individuals’ facial muscles at five to 10 frames per second as they reacted to different displays. The images were fed to a computer network, where artificial-intelligence algorithms assessed each person’s gender and age group and analyzed their expressions for signs of “happiness” and “engagement.”