It's thought by neurobiologists that "hanger" is an old standby survival mechanism from the days when acquiring food wasn't a simple matter of looking up the nearest CVS, but a process that involved a ton of fighting, killing, and -- most importantly -- being a selfish dick with regards to your fellow man. In the days of yore, when times were tough and meals were lean, hanger enabled everyday folk to flip into beast mode and get their rightful share, as opposed to feebly standing in the background watching only the swolest members of the tribe chow down.
Brain Freeze Is The Blood Vessels In Your Head Acting Up
Brain freeze is one of the most painful sensations possible, short of childbirth and reading the news. On the face of it, it's pretty easy to explain. Touching something cold causes a stinging sensation. Ergo, putting something cold inside your head causes your head to be filled with a stinging sensation. Stop us if we're going too fast with all this science jargon.
Except that's not really the case at all. Brain freeze -- or to give its proper name, sphenopalatine ganglioneuralgia -- isn't triggered by cold (such as eating a huge scoop of ice cream), but by the combination of cold and warm immediately after the cold.
When something cold (again, like ice cream) touches the roof of your mouth, it causes the capillaries in your sinuses to cool -- a temperature drop that radiates out to your blood vessels and causes them to narrow, constricting blood flow. If you imbibe something warm immediately afterward, such as a hot drink or even a breath of warmer air, this causes the capillaries to warm and, inversely, your blood vessels to widen, causing all that pent-up blood to be released very quickly.