You can't rate the brain like say "oh, my brain only running at 6%". Cuz your brain is not just one big part itself, its multiple parts joined and working together; a component. So if some random guy comes saying, "my brain is running at 100%!". So he's saying that the speech control part is working non-stop, aka he won't stop talking. Imagine every part working at maximum, fear control and all those- the person will go kookoo. Feel scared, brave, funny, and everything at the same time.

XD Aha! How do we know that?
But it'd be wonderful if we can device a method to point out which section of the brain does what.