Summary

Chapter 4 begins with a discussion of the marvelous attributes of the human brain. For example, the brain is 75 to 80 percent water, Bryson reports, and it is soft, having the consistency of “tofu, soft butter, or slightly overcooked Jell-O pudding” (48). Everything we know about the world is given to us by our brain, although our brain never directly experiences or sees the world. It has no pain receptors and no feelings of its own. The world to our brains is a stream of electrical pulses. A segment of the brain the size of a grain of sand can hold two thousand terabytes of information or all the movies ever made. The brain is also incredibly efficient, Bryson writes, using only 400 calories a day. Neurons, the main cells that make up our brains, are long and stringy to more effectively pass on electrical signals...