Why do we suddenly forget why we walked into a room?

A: Sometimes you get up from your desk because you need scissors and walk into the next room. Suddenly you stop and find your brain has stopped working.

Experts have some explanations for why this happens. For one, our memory depends on context, and at your desk, there are cues, e.g. tape, to remind you of scissors. When you move away from these cues, the memory weakens.

The brain also segments experiences into meaningful episodes. Walking through a doorway can sometimes be like an event boundary, with the brain treating what happened before as belonging to one past episode and what happens next as the start of another. So information associated with a previous episode may become temporarily harder to retrieve.

Experiments have found that in some conditions, people can struggle more to remember an object or instruction after crossing a doorway than after travelling the same distance within a single room. However, walking back through the doorway could restore some of the cues.

Finally, our working memory can keep a limited amount of information readily available, and during the short walk to the other room, other sights and thoughts can push it out of reach.