&gt; During sleep deprivation, he says, “The brain, probably because it is so tired, starts to have difficulties gauging its own level of sleepiness.” Eventually, an exhausted brain gives up on sending you signals that it needs rest. You feel OK precisely because you’re not.<p>If true, I think that&#x27;s the most important point of the article. If you can&#x27;t trust your own brain, you can&#x27;t any claims made by people trying that sort of schedule.<p>Also, the amount of effort you have to put up with in order to even start sleeping like that suggests me that&#x27;s unnatural and unhealthy. We may even have some kind of adaptation for that in the short term. Think cavemen who just lost his shelter and needs to find another in dangerous territory. It&#x27;s conceivable that one could spend a few weeks not sleeping much until conditions improve. Forget about longer term effects, since survival is at stake. So, the brain keeps getting pulled out of sleep due to perceived dangers (in modern times, that&#x27;s the alarm clock). Then it switches off part of the sleep mechanism so that the subject will have a better chance of moving away from danger.