This is interesting, particularly the comments and study just before launching. 

“We wanted the bot to sound as human as possible so it feels like you’re talking to a friend,” Kaplan said. “A beta group texted the number without knowing it was a bot — the true test of authenticity. When the group couldn’t figure it out, we knew we were ready to launch.”

A chatbot is software that responds to your messages using natural language and relies on artificial intelligence to determine what you mean and deliver a tailored reply.

https://www.cnet.com/news/insomniacs-this-chatbot-will-keep-you-company/