The Door

Ever walk into a room with some purpose in mind, only to completely forget what that purpose was?
It turns out, doors themselves are to blame for these strange memory lapses.
Psychologists at the University of Notre Dame have discovered that passing through a
doorway triggers what's known as an event boundary in the mind, separating one set of
thoughts and memories from the next. Your brain files away the thoughts you had in
the previous room and prepares a blank slate for the new locale.

Thank goodness for studies like this. It's not our age, it's that Stupid Door!