Sleep comes in waves
Sleep doesn't build up steadily, it
flows in and out like ocean waves. You've probably felt this yourself. Think
back to the last time you were fighting off sleep. There was probably a moment
when you were struggling to keep your eyes open, then a few monents later you
felt awake and alert. You feel like you've successfully fought off sleep, but
your victory is short lives. Minutes later you are again struggling to keep
your eyes open
In your fight against sleep, you are a lot like a sand castle fighting a
rising tide. A wave comes rushing in, then quickly pulls back. The sand castle
walls may have held up this time, but there is another wave coming. Each wave
weakens the wall, and it is only a matter of time before the sand castle is swepted
out to sea. Similarily, you are hit by a wave of drowsiness and fight it off.
You feel alert again and tell yourself you can drive for another hour. Minutes later
another wave of sleep rushes in and you once again are struggling to keep your eyes open.
The video to the right is a good example of this. In a span of 2 minutes,
the subject of this video will go from being awake, to sleep, to awake again a
total of 6 times. In a few instances, the person will be awake again for only
a few seconds before drifting back to sleep again. Consider this next time you
feel drowsy while driving. In one instant you feel alert, then seconds later
your are asleep, perhaps without even realizing you feel asleep.
Scienctific Background
Scientist explain this phenonom with two concepts. Sleep pressure and
Alerting activities. Sleep pressure is you underlying need for sleep. The longer
you go without sleep, the greater the sleep pressure. Alerting activities are things
that your do to mask the underlying sleep pressure and make you feel more
alert. Talking, exercise and caffeine all make you feel more alert without
reducing your underlying need for sleep. Researchers say these activities
mask you need for sleep.
When you are fighting off sleep, your sleep pressure is roughly equal to
your Alerting activities. In this state, if you do something passive, such
as watching tv, listening to a lecture, reading a book or driving
a car, your will move in and out of a state of sleep depending on what
you are doing and what is happening around you.
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