The Matter of Bathroom Light Avoidance
The light was left off to protect sleep. The knee has now been introduced to the cabinet.
2:17am.
The person gets up. The light stays off. This is intentional. The light, if turned on, would be bright, and bright is associated with awake, and awake is exactly what the night's administration has been working to prevent.
The person navigates the bathroom by memory to protect their sleep.
Memory is confident. Memory has done this before. Memory knows the cabinet is on the left, the edge of the sink is at hip height, the toilet is straight ahead, and the distance is eight steps.
Memory is wrong about six steps.
People avoid turning on a bright bathroom light at night because feeling fully awake seems more dangerous than seeing poorly. This reasoning holds in principle. In practice, it produces a navigation system that performs well in normal conditions and degrades reliably under fatigue, which is when it is most frequently used.
The knee contacts the cabinet.
The sound is brief. The pain is informative. The person is fully awake.
This is not the first time. The cabinet has been in this location since the apartment was occupied. The knee knows the cabinet. The knee meets the cabinet anyway, because the alternate cabinet, the one that memory uses at night, is located slightly to the right of the actual cabinet, in a position that has never corresponded to any physical furniture.
Bathroom Light Avoidance feels harmless once. Repetition turns it into part of the expected bedtime sequence. The sequence now includes: get up, leave light off, locate cabinet by collision, recover, continue.
Skipping the light has become the procedure.
Skipping the knee would require turning on the light.
The person returns to bed. The room is the same temperature it was. Sleep resumes.
The governing rule is satisfied.