Blushing and embarrassment go hand in hand. Feeling flushed is such a natural response to sudden self-consciousness that if it weren't part of an emotionally crippling experience, it could almost be overlooked. But blushing is unique, which is why scientists want to know more about blushing. While the psychology of blushing remains elusive, we do understand the physical process involved. Here's how it works.
Blushing from embarrassment is governed by the same system that activates your fight-or-flight response: the sympathetic nervous system. This system is involuntary, meaning you don't actually have to think to carry out the processes. In contrast, moving your arm is a voluntary action; You have to think about it, no matter how fleeting the thought is. This is good, because if moving your arm was involuntary, people would end up buying a lot of stuff they don't want at auctions.