Your Brain: The Missing Manual

Chapter 7. Reason

In the world of logic, it's easy to fault the human brain. For most of the day, we walk around with our critical brains powered down. We buy exotic exercise equipment from late-night infomercials. We pass around emails that link lung cancer to chewing gum. We send checks to pleasant Nigerian gentlemen with odd banking problems. Studies that track down the victims of these hoaxes don't just find bewildered seniors and lonely housewives—they also turn up lawyers, investment bankers, teachers, and other people who are in the business of thinking straight.

Sadly, the brain's shoddy thinking is more than a bad habit—it's an instinctive and automatic way of perceiving the world. When we hear a discussion, we filter out everything but the arguments we recognize and the ideas we like. Facts seep out of our brains like warm jello. We dive into health fads, fashion trends, new-fangled hobbies, political movements, and every sort of cobbled-together superstition that passes our way, all on the very thinnest of grounds. And when asked to explain our behavior, we look deep into our hearts and make something up. Quite simply, humans are masters of irrational behavior.

In this chapter, you'll learn why we often fall for sloppy thinking and fuzzy arguments. You'll see how quick assumptions, generalizations, and pre-judices aren't just bad habits, they're also part of a critical set of life skills that helped our remote ancestors avoid ending up as another animal's dinner. Along ...