What will it take to make AI sound human?

Conversation fillers such as "hmm" and "uh-huh" may seem like insignificant parts of human conversation, but they're critical to improving communication between humans and artificial intelligence. So argues Alan Black, a professor in the Language Technologies Institute at the Carnegie Mellon School of Computer Science, who specializes in speech synthesis and ways to make artificially intelligent speech sound more real. Both Siri and Cortana incorporate aspects of Black's work, he says. But for t...