can't hear us laugh at their joke but we still laugh because it triggers the response. My guess is during a movie it's probably more about conditioning.

Probably why you don't see clapping after church choir performances or during conference, but laughing is ok. We've been conditioned that one is ok and the other is not even though it is a live performance.

So some people clap in movie theaters and some church or choir attendees don't clap after such live performances in order to show their appreciation.

Just lots of conditioning and habits at play.