The broken escalator phenomenon, also known as the Walker effect, is the sensation of losing balance or dizziness reported by some people when stepping onto an escalator which is not working. It is said that there is a brief, odd sensation of imbalance, despite full awareness that the escalator is not going to move.
It has been shown that this effect causes people to step inappropriately fast onto a moving platform that is no longer moving, even when this is obvious to the participant.
Even though subjects are fully aware that the platform or escalator is not moving now, parts of their brains still act on previous experience gained when it was moving, and so misjudge how to step onto it. Thus, this effect demonstrates the separateness of the declarative and procedural functions of the brain.