Radvansky tested this by having students examine a box containing objects such as red cubes and blue spheres. Then, the students tried to remember what those objects were after either walking into another room or just walking that same distance without crossing any doorways. The results were so dramatic that researchers proceeded to redub doorways "event erasers," a name so badass that it is what we're going to call doorways from now on.
"Son? I'm sorry, but I never had a son."
And the effect of doorways is so strong that you don't even have to physically move for those bastards to put the kibosh on your memory. In another experiment, the researchers had people sit at a computer and do the same test, where the new "room" was just an animation on the screen. The effect was exactly the same -- every time their avatar crossed a virtual doorway, their ability to recall objects fell down the forgetting well.
However, our door-riddled culture is not doomed to a collective Memento disease. Saying things out loud as you pass the doorway can apparently thwart the effect. It stands to reason, really -- even if you managed to forget that you entered the office exclaiming that you need to buy cream for your genital warts, you'd probably be reminded plenty of times.
"Hey there, Jerry! Heard you had a big ol' case of Braille-dick."