Eli5: Why do we notice a delay on a call when looking at the other person but not when we can’t see them?

Question

If I’m looking at someone and call their phone there is an obvious delay and it’s weird, if I’m driving or otherwise talking to someone not with me the delay isn’t noticeable, why is that?

In: Technology

Answer 1

There’s always that delay in a phone call, if the person isn’t in your line of sight your brain just doesn’t have any other data. When you can see your friend’s lips move and the sound is out of sync, your brain says “Dude, that’s weird…”