>>14041841It's common in mammals that to make one's midsection open and vulnerable to another is a signal of trust or submission. Instinctively this area of our body if something we would value over others. For instance if threatened you use your arms to block it, valuing your torso over your arms. You are essentially giving this person to option to kill you, but since you are offering your submission they could be valuable in some capacity. This is why crossing your arms, especially in front of your boss, can be seen as a hostile gesture.
