Like crying when you are sad, turning red when you are embarressed, or heart pounding when you are nervous. Why do these mental/emotional things cause physical reactions?
Fight/flight responses prepare you to do exactly that–either fight or flee. Blood flow is diverted from the organs to the muscles, the heart pumps faster to deliver more oxygen, etc. Any emotion related to fear/anxiety is part of this.
As far as laughing and crying, I really don’t know.
[QUOTE=Sattua]
Blood flow is diverted from the organs to the musclesQUOTE]
But why does getting embarrassed cause it?
I would guess that perhaps, in evolutionary terms, the physical reaction is really the fundamental part of these emotional states. The mental effects could have come along more recently, after we had developed minds worthy of speaking of, and bent pre-existing reactions to new purposes.
I don’t know what embarrassment corresponds to that might be useful for a relatively unintelligent animal.
The cat slinks off after falling off the windowsill knowing that we will laugh at it, and attempt to catch it for our supper.