Onstage at I/O 2018, Google showed off a jaw-dropping new capability of Google Assistant: in the not too distant future, it’s going to make phone calls on your behalf. CEO Sundar Pichai played back a phone call recording that he said was placed by the Assistant to a hair salon. The voice sounded incredibly natural; the person on the other end had no idea they were talking to a digital AI helper. Google Assistant even dropped in a super casual “mmhmmm” early in the conversation.

Pichai reiterated that this was a real call using Assistant and not some staged demo. “The amazing thing is that Assistant can actually understand the nuances of conversation,” he said. “We’ve been working on this technology for many years. It’s called Google Duplex.”

Duplex really feels like next-level AI stuff, but Google’s chief executive said it’s still very much under development. Google plans to conduct early testing of Duplex inside Assistant this summer “to help users make restaurant reservations, schedule hair salon appointments, and get holiday hours over the phone.”

Pichai says the Assistant can react intelligently even when a conversation “doesn’t go as expected” and veers off course a bit from the given objective. “We’re still developing this technology, and we want to work hard to get this right,” he said. “We really want it to work in cases, say, if you’re a busy parent in the morning and your kid is sick and you want to call for a doctor’s appointment.” Google has published a blog post with more details and soundbites of Duplex in action.

“The technology is directed towards completing specific tasks, such as scheduling certain types of appointments. For such tasks, the system makes the conversational experience as natural as possible, allowing people to speak normally, like they would to another person, without having to adapt to a machine.” Google envisions other use cases like having Assistant call businesses and inquire about their hours to help keep Maps listings up to date. The company says it wants to be transparent about where and when Duplex is being used, as a voice that sounds this realistic and convincing is certain to raise some questions.

In current testing, Google notes that Duplex successfully completes most conversations and tasks on its own without any intervention from a person on Google’s end. But there are cases where it gets overwhelmed and hands off to a human operator. This section on the ins and outs of Duplex is very interesting: