How We Decide Read Online Free PDF

starts doing irresponsible things. The mundane choices of everyday life become excruciatingly difficult. It's as if his very personality—the collection of wants and desires that defined him as an individual—had been systematically erased. His loved ones say it's like living with a stranger, only this stranger has no scruples.
    The crucial importance of our emotions—the fact that we can't make decisions without them—contradicts the conventional view of human nature, with its ancient philosophical roots. For most of the twentieth century, the ideal of rationality was supported by scientific descriptions of human anatomy. The brain was envisioned as consisting of four separate layers, stacked in ascending order of complexity. (The cortex was like an archaeological site: the deeper you dug, the farther back in time you traveled.) Scientists explained the anatomy of the human brain in this manner: At its bottom was the brain stem, which governed the most basic bodily functions. It controlled heartbeat, breathing, and body temperature. Above that was the diencephalon, which regulated hunger pangs and sleep cycles. Then came the limbic region, which generated animal emotions. It was the source of lust, violence, and impulsive behavior. (Human beings shared these three brain layers with every other mammal.) Finally, there was the magnificent frontal cortex—the masterpiece of evolution—which was responsible for reason, intelligence, and morality. These convolutions of gray matter allowed each of us to resist urges and suppress emotions. In other words, the rational fourth layer of the brain allowed us to ignore the first three layers. We were the only species able to rebel against primitive feelings and make decisions that were dispassionate and deliberate.
    But this anatomical narrative is
false.
The expansion of the frontal cortex during human evolution did not turn us into purely rational creatures, able to ignore our impulses. In fact, neuroscience now knows that the opposite is true: a significant part of our frontal cortex is involved with emotion. David Hume, the eighteenth-century Scottish philosopher who delighted in heretical ideas, was right when he declared that reason was "the slave of the passions."
    How does this emotional brain system work? The orbitofrontal cortex (OFC), the part of the brain that Elliot was missing, is responsible for integrating visceral emotions into the decision-making process. It connects the feelings generated by the "primitive" brain—areas like the brain stem and the amygdala, which is in the limbic system—to the stream of conscious thought. When a person is drawn to a specific receiver, or a certain entrée on the menu, or a particular romantic prospect, the mind is trying to tell him that he should choose that option. It has already assessed the alternatives—this analysis takes place outside of conscious awareness—and converted that assessment into a positive emotion. And when he sees a receiver who's tightly covered, or smells a food he doesn't like, or glimpses an ex-girlfriend, it is the OFC that makes him want to get away. (
Emotion
and
motivation
share the same Latin root,
movere,
which means "to move.") The world is full of things, and it is our feelings that help us choose among them.
    When this neural connection is severed—when our OFCs can't comprehend our own emotions—we lose access to the wealth of opinions that we normally rely on. All of a sudden, you no longer know what to think about the receiver running a short post pattern or whether it's a good idea to order the cheeseburger for lunch. The end result is that it's impossible to make decent decisions. This is why the OFC is one of the few cortical regions that are markedly larger in humans than they are in other primates. While Plato and Freud would have guessed that the job of the OFC was to
protect
us from our emotions, to fortify reason against feeling, its actual