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and telling him to stop,” Damasio wrote. But he and his fellow researchers just stood there watching. Finally Damasio interrupted the man’s musings and just assigned him a date to return. Without a pause, the man said, “That’s fine” and went away.
     
    “This behavior is a good example of the limits of pure reason,” Damasio writes in his book
Descartes’ Error: Emotion, Reason, and the Human Brain
. It’s an example of how lack of emotion leads to self-destructive and dangerous behavior. People who lack emotion don’t lead well-planned logical lives in the manner of coolly rational Mr. Spocks. They lead foolish lives. In the extreme cases, they become sociopaths, untroubled by barbarism and unable to feel other people’s pain.
     
    Out of these and other experiences Damasio developed a theory, which he called the “somatic marker hypothesis,” on the role of emotion in human cognition. Parts of the theory are disputed—scientists differ about how much the brain and the body interact—but his key point is that emotions measure the value of something, and help unconsciously guide us as we navigate through life—away from things that are likely to lead to pain and toward things that are likely to lead to fulfillment. “Somatic markers do not deliberate for us. They assist the deliberation by highlighting some options (either dangerous or favorable), and eliminating them rapidly from subsequent consideration. You may think of it as a system for automated qualification of prediction, which acts, whether you want it or not, to evaluate the extremely diverse scenarios of the anticipated future before you. Think of it as a biasing device.”
    As we go about our day, we are bombarded with millions of stimuli—a buzzing, blooming confusion of sounds, sights, smells, and motions. And yet amidst all this pyrotechnic chaos, different parts of the brain and body interact to form an Emotional Positioning System. Like the Global Positioning System that might be in your car, the EPS senses your current situation and compares it to the vast body of data it has stored in its memory. It reaches certain judgments about whether the course you are on will produce good or bad outcomes, and then it coats each person, place, or circumstance with an emotion (fear or excitement, admiration or repugnance) and an implied reaction (“Smile” or “Don’t smile”; “Approach” or “Get away”) that helps us navigate our days.
    Let’s say someone touches your hand across a restaurant table. Instantly, the mind is searching the memory banks for similar events. Maybe there was a scene in
Casablanca
when Humphrey Bogart touched Ingrid Bergman’s hand. Maybe there was a date in high school long ago. There was a distant memory of Mom, reaching across and holding hands with you during a childhood visit to McDonald’s.
    The mind is sorting and coding. The body is responding. The heart speeds. Adrenaline rises. A smile opens up. Signals are flowing from body and brain and back again in quick intricate loops. The brain is not separate from the body—that was Descartes’ error. The physical and the mental are connected in complex networks of reaction and counter-reactions, and out of their feedback an emotional value emerges. Already the touch of the hand has been coated with meaning—something good, something delicious.
    An instant later, a different set of loops open. This is the higher set of feedback routes between the evolutionarily older parts of the brain and the newer, more modern parts such as the prefrontal cortex. This set of information flow is slower, but more refined. It can take the reactions that have already been made by the first system and make finer distinctions among them. (“This hand reaching to touch me across the table is not quite like my mother’s hand. It’s more like the hand of other people I wanted to have sex with.”) It can also flash warnings that lead to intelligent restraint. (“I’m so