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and eyes, breathing, heart rate, sleep, arousal, and digestion. This stuff is really important, but
    you don’t usually notice it happening. A bit higher up, the hypothalamus also controls basic
    processes that are important to life, but it gets the fun jobs. Its responsibilities include the release of
    stress and sex hormones and the regulation of sexual behavior, hunger, thirst, body temperature, and
    daily sleep cycles.
    Emotions, especially fear and anxiety, are the responsibility of the amygdala . This almond-
    shaped brain area, located above each ear, triggers the fight-or-flight response that causes animals to
    run away from danger or attack its source. The nearby hippocampus stores facts and place
    information and is necessary for long-term memory. The cerebellum , a large region at the back of the
    brain, integrates sensory information to help guide movement.
    Did you know? Is your brain like a computer?
    People have always described the brain by comparing it to the latest technologies,
    whether that meant steam engines, telephone switchboards, or even catapults. Today people

    tend to talk about brains as if they were a sort of biological computer, with pink mushy
    “hardware” and life-experience-generated “software.” But computers are designed by
    engineers to run like a factory, in which actions occur according to an overall plan and in a
    logical order. The brain, on the other hand, works more like a busy Chinese restaurant: it’s
    crowded and chaotic, and people are running around to no apparent purpose, but somehow
    everything gets done in the end. Computers mostly process information sequentially, while
    the brain handles multiple channels of information in parallel. Because biological systems
    developed through natural selection, they have layers of systems that arose for one purpose
    and then were adopted for another, even though they don’t work quite right. An engineer
    with time to get it right would have started over, but it’s easier for evolution to adapt an old
    system to a new purpose than to come up with an entirely new structure.
    Sensory information entering the body through the eyes, ears, or skin travels in the form of spikes
    to the thalamus , in the center of the brain, which filters the information and passes it along, as more
    spikes, to the cortex . This is the largest part of the human brain, making up a little over three-fourths
    of its weight, and it is shaped like a large crumpled-up comforter that wraps the top and sides of the
    brain. The cortex originated when mammals first showed up, about 130 million years ago, and it takes
    up progressively more and more of the brain in mice, dogs, and people.
    Scientists divide the cortex into four parts called lobes. The occipital lobe , in the back of your
    brain, is responsible for visual perception. The temporal lobe , just above your ears, is involved in
    hearing and contains the area that understands speech. It also interacts closely with the amygdala and
    hippocampus and is important for learning, memory, and emotional responses. The parietal lobe , on
    the top and sides, receives information from the skin senses. It also puts together information from all
    the senses and figures out where to direct your attention. The frontal lobe (you can probably guess
    where that’s located) generates movement commands, contains the area that produces speech, and is
    responsible for selecting appropriate behavior depending on your goals and your environment.
    Together, the combination of these abilities in your brain determines your own individual way of
    interacting with the world. In the rest of the book, we’ll take these abilities in turn and tell you what’s
    known about how the brain accomplishes its everyday tasks.
    Chapter 4
    Fascinating Rhythms: Biological Clocks and Jet Lag
    Remember when you were a kid and Uncle Larry bet that you couldn’t walk and chew gum at the
    same time? It may have seemed like a lame bet, but when you