God Soul Mind Brain

property makes sense, receives confirmation, asks for further details, probes for consistency, tests for resonance, and in this way builds a rich model of the other person’s mental state. We use the idiosyncrasies of our own brains to construct a model of another mind.

    If this is the correct general description of how the brain constructs a model of another mind, then perhaps it explains why we tend to perceive other people through the filter of our own selves. We judge other people to have the same motivations and foibles. A trustworthy person tends to trust others because, in building models of other people’s minds, he relies on the quirks of his own mind. An untrustworthy person tends to suspect that everyone is cheating him. A happy person assumes that other people are happy. A person with a grotesque sense of humor assumes, annoyingly, that everyone else shares the same sense of humor. The same mechanism might explain why angry people, in their religious moments, when their perceptual machinery constructs a model of God’s mind, tend to perceive God to be a force of furious punishment, and generous people perceive God to be a source of generosity and love. Certainly the Hellenic Greeks saw their gods as mirrors of their own human foibles, appetites, and decencies. In the mirror hypothesis, the minds that we perceive around us are constructed out of the raw materials of our own brains.

Chapter 9

    Down the rabbit hole: Emotion in the depths of the brain

    Imagine that somebody with dubious intentions has implanted half a dozen electrodes into your brain. By passing electric current down one or another electrode the evildoer can manipulate your emotions, making you furious, or sad, or hungry, or sexually aroused, or frightened, switching from one emotion to another instantaneously with the press of a button. Technically this Frankensteinian experiment is possible, although it would not pass a modern ethics review. The owner of the button box could control you remotely.

    At the base of the brain lies a small nucleus, dense with neurons, called the hypothalamus. The emotions are on tap in the hypothalamus. The emotional content of the hypothalamus was discovered in the 1950s in rats, and experiments over subsequent decades and in many labs revealed an entire repertoire of emotional states. The hypothalamus is a primitive structure in the strict evolutionary sense; it is shared by so many branches of the mammalian tree that it probably was present in an ancestral animal. Rats, cats, dogs, monkeys, people—we all share a similar neuronal architecture that supports our emotions and therefore we probably have similar emotional experiences.

    For example, stimulation in one part of the hypothalamus causes a rat to eat, as if the animal is experiencing hunger. As long as the stimulating current is left on, for minutes at a time, the animal stuffs its face with the nearest food. As soon as the stimulating current stops, the animal spits out the food, drops the pellet it is holding, and shows every sign of being full. Turn the current back on, and the eating starts again. This nucleus was a target of great interest in the 1960s, when scientists tried to identify it in humans and destroy it as a way to reduce the hunger drive and treat obesity. The experiments were of limited success. The ethics of so-called psychosurgery, mucking with the brain to change a person’s behavior, are dubious to say the least, and this type of manipulation is no longer legal.

    Stimulation of another location in the hypothalamus, just beside the hunger nucleus, causes the animal to mate with anything nearby that looks alive. This experiment has been tried in a range of animals including mice, rats, and monkeys, with similar results. Sexual arousal is controlled by this specific location in the hypothalamus.

    Stimulation of a third location in the hypothalamus with an electrode causes an animal to go into a rage—a pure killing rage—shrieking and biting. This stimulation-evoked rage is termed “sham rage,” but there is nothing sham about it, other than the strange fact that it starts and stops instantaneously with the stimulating current. In theory, if you had an electrode in your own rage nucleus and could turn it on and off at will, you might be able to use it strategically on the football gridiron, or in a boxing ring, as a technologically advanced form of doping.

    Another location makes the animal act in a nurturing way,