5 exi
My father, when I was 9, bought a brain stimulator in the 1990s. A grid with electrodes to put on the head and a controller where you could change the power of the current and the intervals of "strokes", and much more apparently. I studied badly, my father decided to check on me. I put a small current to start and apparently not impressed by the result, I turned the pen into an extreme position. I lost consciousness, I woke up quickly enough... And I started learning better, but I think the effect was achieved by the reluctance to never wear it on myself.