Here's why Google's new AI assistant tells you it's a robot -- even if it sounds human

Silicon Valley's quest for artificial intelligence has led it to build self-driving cars, drones, and robots that can do backflips. But often that journey has come down to something much more prosaic, such as ordering a pizza -- or booking a restaurant reservation. Duplex is the company's next-generation virtual helper. When the company first showcased it at its developer conference in May, it engaged in conversation so lifelike -- complete with humanlike "ums" and pauses -- that the person on the other end of the call couldn't tell that the speaker was just software. Some asked whether the interaction was fake.