Even the most nimble-minded among us have pondered that question after walking into a room with some purpose in mind — to get something, perhaps? — only to blank on what that purpose was. Now a new study suggests that it’s the very act of walking through a doorway that causes these strange memory lapses.

“Entering or exiting through a doorway serves as an ‘event boundary’ in the mind, which separates episodes of activity and files them away,” said lead researcher Gabriel Radvansky, a psychologist at the University of Notre Dame. “Recalling the decision or activity that was made in a different room is difficult because it has been compartmentalized.”

In our minds, like in the movies, threshold-crossing signals the end of a scene.

via Forget Why You Walked in a Room? Doorways to Blame, Study Finds | LiveScience.