In “The A. I. Anxiety,” Joel Achenbach discusses the ideas of philosopher Nick Bostrom, physicist Max Tegmark, and others about A. I. or artificial intelligence. “Big-name scientists worry that runaway artificial intelligence could pose a threat to humanity. Beyond the speculation is a simple question:  Are we fully in control of our technology?” Which is the greater threat … that machines will become superintelligent or superstupid?