Seth Fishman, literary agent, did a very comprehensive Reddit AMA.

I’ve taken to writing blindfolded, rolling my head around.  Speaking gibberish, sounding out vowels and mashes of consonants.  All of this, by the way, for a novel (maybe).  Disclosing some history: I wrote my last one, my first first one–as my true first novel is 50,000 words of cliches and will forever live inside a box neath my pillow & bed–in 72 hours, first draft, sleeping six hours total.  I feel like the fugue created by my body struggling to maintain helped me be something really desperate, which fit what was happening in the narrative.  Roundabout way of asking: You perform your writing?  I like to.  Yell at me some, please.

p.s. no sleep is midas touch

p.p.s. The Pirahã people have no history, no descriptive words and no subordinate clauses.