Counting duh

Duh! The Stupid History of the Human RaceFinally a little data to help determine if we’re losing our mind.

How many ‘Doh!’ moments does the average person have?
“We’ve all run upstairs to get something, only to arrive and realise we’ve forgotten what we went up there for? But just how common are these moments of absent-mindedness? According to a new study by Icelandic psychologists, healthy people commit an average of 6.4 such lapses or “action slips” a week.”

Wiki says Duh is an American English slang exclamation that is used to express disdain for someone missing the obviousness of something.