I've noticed the night effect for a long time too, and while the lack of interruptions might have something to do with it, I don't think it nearly explains my 3x boost in productivity.<p>I think there's something biological going on as well. Around 1 or 2 am, I sometimes get a bang of energy and creativity that I never get during the day. It's the "second wind," the injection (possibly) of cortisol and other stress hormones that cause my body to go into stress-protection mode. I become hypervigilant, which causes fewer bugs. I think more quickly, writing code faster and coming up with amazing design ideas instantly.<p>If you think about this from an evolutionary perspective, it makes perfect sense-- in the animal world, when you become stressed (i.e., a tiger comes up behind you, or you get exhausted looking for food) the outcome is binary: either you die or you live. So the body does extraordinary things to keep you alive, like make you temporarily smarter and more focused.<p>Over hundreds of thousands of years, perhaps, the body has developed in such a way that the lack of sleep for some number of hours (for me, almost exactly sixteen or seventeen hours) triggers the release of stress hormones which sacrifice the body's current state for mental and physical agility.<p>When will someone figure out how to hack my brain to make it like that all the time, without the nasty side effects (sleep deprivation) the next day?<p>More info:<p><a href="http://www.medscape.com/viewarticle/502825" rel="nofollow">http://www.medscape.com/viewarticle/502825</a><p><a href="http://en.wikipedia.org/wiki/Cortisol" rel="nofollow">http://en.wikipedia.org/wiki/Cortisol</a><p><a href="http://en.wikipedia.org/wiki/Norepinephrine" rel="nofollow">http://en.wikipedia.org/wiki/Norepinephrine</a><p>I should do more research on this.