In January, Google's chief executive, Sundar Pichai, claimed in an interview that AI "is more profound than, I dunno, electricity or fire." Day-to-day developments, though, are more mundane. Recently Pichai stood onstage in front of a cheering audience and proudly showed a video in which a new Google program, Google Duplex, made a phone call and scheduled a hair salon appointment. The program performed those tasks well enough that a human at the other end of the call didn't suspect she was talking to a computer. Assuming the demonstration is legitimate, that's an impressive (if somewhat creepy) accomplishment.

The dream of artificial intelligence was supposed to be grander than this -- to help revolutionize medicine, say, or to produce trustworthy robot helpers for the home. The reason Google Duplex is so narrow in scope isn't that it represents a small but important first step toward such goals. The reason is that the field of A.I. doesn't yet have a clue how to do any better. As Google concedes, the trick to making Google Duplex work was to limit it to "closed domains," or highly constrained types of data (like conversations about making hair salon appointments), "which are narrow enough to explore extensively." Google Duplex can have a human-sounding conversation only "after being deeply trained in such domains."