"...how do I determine the mass of grey matter in my right anterior prefrontal cortex without hurting myself..."

Not necessary for YOU to do it....it's for those who want to know about you. We have our methods!!

"Weigh your head while trying to introvert...?"

ummm.. introSPECT?...(besides, SINS is a closet extrovert)
There are traffic signs around here that say "Please do not block intersection"...I have this mad urge to change them to 'introspection'.