Definition
- Habituation
- Habituation is the process by which the brain learns to stop responding to a repeated stimulus that carries no consequence. In the context of alarms, it is why a tone that reliably woke you in week one stops working by week four, regardless of how loud it is.
Why alarms stop working
Your brain filters sensory input constantly, and one of its main criteria is novelty. A sound that has occurred many times without anything important following it gets categorised as background and stops triggering arousal during light sleep.
Crucially, habituation applies to volume as well as to tone. Making an alarm louder resets the novelty temporarily, but you adapt to the new level too — which is why escalating volume buys progressively less time.
What counters it
Variation and consequence. A stimulus that changes unpredictably cannot be filtered as reliably, and one that is followed by something requiring action does not get categorised as ignorable.
This is the reasoning behind rotating alarm sounds, and behind mission alarms that vary what they demand each morning rather than presenting the identical task indefinitely.