5301991f_and_The_Art_of_Breaking_Things__detailed_explanation
[signal] Laughter [part of body] mouth [possible meaning(s)] relaxation [detailed explanation] 
Laughter deserves a section in its own right because its such an interesting area. In terms of body language genuine laughter is a sign of relaxation and feeling at ease. Natural laughter can extend to all the upper body or whole body. The physiology of laughter is significant. Endorphins are released. Pain and stress reduces. Also vulnerabilities show and can become more visible because people’s guard drops when laughing.
“I pretty much try to stay in a constant state of confusion just because of the expression it leaves on my face.” – Johnny Depp | Zen and The Art of Breaking Things
detailed explanation