Sally Adee, a science writer lucky enough to try a DARPA experiment that uses targeted electrical stimulation of the brain during training exercises to induce flow state for a New Scientist article, has some really fascinating things to say about what it was like:
The experience wasn't simply about the easy pleasure of undeserved expertise. When the nice neuroscientists put the electrodes on me, the thing that made the earth drop out from under my feet was that for the first time in my life, everything in my head finally shut the fuck up.
The experiment I underwent was accelerated marksmanship training on a simulation the military uses. I spent a few hours learning how to shoot a modified M4 close-range assault rifle, first without tDCS and then with. Without it I was terrible, and when you're terrible at something, all you can do is obsess about how terrible you are. And how much you want to stop doing the thing you are terrible at.
Then this happened:
The 20 minutes I spent hitting targets while electricity coursed through my brain were far from transcendent. I only remember feeling like I had just had an excellent cup of coffee, but without the caffeine jitters. I felt clear-headed and like myself, just sharper. Calmer. Without fear and without doubt. From there on, I just spent the time waiting for a problem to appear so that I could solve it.
It was only when they turned off the current that I grasped what had just happened. Relieved of the minefield of self-doubt that constitutes my basic personality, I was a hell of a shot. And I can't tell you how stunning it was to suddenly understand just how much of a drag that inner cacophony is on my ability to navigate life and basic tasks. [...]
Me without self-doubt was a revelation. There was suddenly this incredible silence in my head; I've experienced something close to it during 2-hour Iyengar yoga classes, but the fragile peace in my head would be shattered almost the second I set foot outside the calm of the studio. I had certainly never experienced instant zen in the frustrating middle of something I was terrible at. There were no unpleasant side effects. The bewitching silence of the tDCS lasted, gradually diminishing over a period of about three days. The inevitable reintroduction of self-doubt and inattention to my mind bore heartbreaking similarities to the plot of Flowers for Algernon.
I hope you can sympathize with me when I tell you that the thing I wanted most acutely for the weeks following my experience was to go back and strap on those electrodes. I also started to have a lot of questions. Who was I apart from the angry little bitter gnomes that populate my mind and drive me to failure because I'm too scared to try? And where did those voices come from? Some of them are personal history, like the caustically dismissive 7th grade science teacher who advised me to become a waitress. Some of them are societal, like the hateful ladymag voices that bully me every time I look in a mirror. Invisible narrative informs all my waking decisions in ways I can't even keep track of.
What would a world look like in which we all wore little tDCS headbands that would keep us in a primed, confident state free of all doubts and fears? Wouldn't you wear the shit out of that cap? I certainly would. I'd wear one at all times and have two in my backpack ready in case something happened to the first one.