[albedo]

The way that adaptation works (warning: simplifying a bit here) is that your brain wants you to get restful sleep when you aren't allowing it to. In this situation, its default strategy is to cause you to feel the effects of sleep deprivation in order to induce sleep. If you successfully resist this urge, only going to sleep at certain times, and follow a schedule fairly strictly, then your brain will give up after a week or two, and will learn to just take whatever it can get during those time slots (i.e. go directly into REM sleep).

After a while of doing this (adaptation), you will get most or all of the sleep you need, just from naps, and you will no longer feel sleep deprivation.

Check out the book "Ubersleep" written by Pure Doxyk, someone who has successfully done long-term polyphasic sleep, for details on this model of sleep.

[FR6]

albedo you have made a excellent summary! When I tried it, I slept 20 minutes every 4 hours and at the end when my system had adapted, I woke up automatically after 20 minutes even before my alarm went off and full of energy as if I slept 10 hours. But after 4 hours, I was completely exhausted and I really needed my 20 minutes of sleep.