In another thread, I mentioned that some actors fake "crying" by fake "laughing." The I wondered if it would be possible to tell the difference if we could only hear or only see the actor.

I was able to prove my theory, somewhat, the other day. Husband and I were sitting in bed and we started wrestling. For some reason, I got the giggles and started laughing hysterically as he whacked me with his pillow and then held it over my head. As I was laughing, I realized the sound was VERY similar to someone crying, and that my shoulders were heaving the same way they would if I were emotional. I can't verify whether the facial expression would pass, but it certainly FELT as if the two emotions would produce very similar responses. Which makes sense, since they both are highly charged emotionally and also include some measure of a loss of control. A good long laugh is a good aerobic workout, I've never noticed the same with a good cry, but that's probably because I was more caught up in the emotion rather than the physical sensations, but maybe this is why a good cry and a good laugh both leave us feeling refreshed?