Nootropics, the new staple ‘brain enhancers’ in Silicon Valley that purport to increase productivity and perception, exist in an unregulated legal gray area in the U.S. In Colombia, you can pick up even the shadiest kinds over the counter. I did just that. In the months before a recent trip to Colombia, off to visit an expat friend living there, I had been hearing about nootropics. Or “smart drugs,” as they’re referred to. Brain enhancers. Mental magic. Depending on which site you’ve read that’s proclaimed them the new “It” drug for bio-hackers of every stripe, all roads lead to the...