How much do actors know about body language? Are they generally taught to use body language in a way consistent with what they're saying and expressing with their faces? (If so, does this mean that watching TV shows or movies muted could be a good way to practice reading body language?)
In which case would this be preferable to live human interaction? It lacks the immediate salient feedback and strong incentives of a social setting. The editing and narrative would be distracting and watching a muted movie sounds (or rather, looks) quite boring.
If it's worth saying, but not worth its own post, even in Discussion, it goes here.