How is stupidity judged?

Question

I mean, is it judged by ones actions, or by their brain capacity?

Answer 1

i'd say mostly by actions.

people usually know what is wrong or "stupid" but they do it anyways.  

brain capacity is just measured by some standard that some guy came up with.  

ever heard of a savant?  they are some of the most brilliant people in the world even if they only have a talent in one thing like music.

Answer 2

By the results of the actions, or the potential results:

Class 1 stupidity - embarrassing to yourself, and maybe the people who hang out with you.  Nobody get hurt beyond a scrapes, getting baned up, maybe a broken bone.  You trip and fall flat on your face because you are trying to show off look cool, for example.

Class 2 stupidity - significant risk of your own life.  You do something that potentially could result in you being nominated for a Darwin Award.  Bonus points if it's caught on film.

Class 3 stupidity - a damned good chance that several or many people could be maimed or killed, especially if it is easily preventable with a little work or forethought.  Driving while drunk is a classic example.  No bonus points are available.  And you deserve a tombstone that tells the world what you did.