“Todd Huffman is a biohacker. His hair is often dyed some primary color or another; his appearance is otherwise indistinguishable from a lumberjack. Some years ago, Todd ordered a small neodymium magnet in the mail. He sterilized the magnet, sterilized a surgical knife, sterilized his hand, and implanted the magnet in his fingers. Now Todd feels magnetic fields. The magnet tugs when exposed to electromagnetic fields, and his nerves register this. Information normally invisible to humans is now streamed to his brain via the sensory pathways of his fingers. His perceptual world expanded the first time he reached for a pan on his electric stove. The stove casts off a large magnetic field (because of the electricity running in a coil). He hadn’t been aware of that tidbit of knowledge, but now he can feel it. Reaching out, he can detect the electromagnetic bubble that comes off of a power cord transformer (like the one to your laptop). It’s like touching an invisible bubble, one with a shape that he can assess by moving his hand around. The strength of the electromagnetic field is gauged by how powerfully the magnet moves inside his finger. Because different frequencies of magnetic fields affect how the magnet vibrates, he ascribes different qualities to different transformers—in words like ‘texture’ or ‘color.’”

But Eagleman goes far deeper than just bio-hacking (interesting as it is) in this book—his enlightening metaphors provide insight into neural processes of all sorts, especially about the competing processes of sensory neurons. Who knew that our ability to see and feel could be equated to a form of neural colony building by our hands and eyes?  We particularly liked the section on why young brains are so much more plastic than older brains—perhaps surprisingly, it’s not all bad news for the mature amongst us. As Eagleman notes: “There’s a trade-off between adaptability and efficiency: as your brain gets good at certain jobs, it becomes less able to tackle others… To get good at one thing is to close the door on others. Because you possess only a single life, what you devote yourself to sends you down particular roads, while the other paths will forever remain untrodden by you. Thus, I began this book with one of my favorite quotations from the philosopher Martin Heidegger: ‘Every man is born as many men and dies as a single one.’”