Twice a week at a senior care facility in Singapore, a few dozen elderly men and women with dementia gather in a large sunlit room with Dexie, a humanoid robot, who leads their morning exercise session. “Open and close your hands. Hold both arms up,” Dexie instructs. “We will do this eight times. 1-2-3-4-5-6-7-8. Good!” Since Dexie arrived at The Salvation Army Peacehaven Jade Circle Arena two years ago, residents look forward to the robot leading their exercises, bingo, and sing-along sessions,...