The best, most human-like AI voice chat I've seen yet is Sesame (www.sesame.com). It has delays, but fills them very naturally with normal human speech nuances like "hmmm", "uhhh", "hold on while I look that up" etc. If there's a longer delay it'll even try to make a bit of small talk, just like a human conversation partner might.
> The person doing the speaking is thought to be communicating through the "front channel" while the person doing the listening is thought to be communicating through the "backchannel”
When learning Japanese in Japan, I figured out one way to sound more native was to just add interjections like “Eeee?” (really?) and “Sou desu ka?” (is that so?) while the other person was talking. Makes it sound like you are paying attention and following what they are saying.
