God Soul Mind Brain

the errors. You actually feel a tinge of embarrassment. You are experiencing the emotional state that seems appropriate for the speaker.

    You watch your favorite boxer punch out an opponent on TV. You find yourself making small but emphatic boxing motions and grunts.

    You watch someone eating a hamburger—you feel hungry. The sight of the hamburger itself probably contributes, but the sight of someone greedily devouring it adds to your own craving.

    You have a conversation with an outgoing, friendly person—for the rest of the day you feel jazzed and have a glow of sociability about you.

    Mirror neurons in a small spot in the motor cortex are just the beginning. They hardly scratch the surface. When you watch another person, vast tracts of your brain are set in action, recreating the mental state of that person. It is as if you are putting yourself in the place of the other person, revving up your motor circuits, your emotional circuits, your decision circuits, not strongly enough to force you to imitate in lock step with the other person, but enough to give you a flavor of the other person’s mind—and to subtly bias you toward behaving in a similar way. In mental imitation, your brain is mirroring other brains.

    The idea that Brain A understands Brain B by mirroring the state of Brain B has been hailed as a fundamental breakthrough. Some theoreticians have said, in effect, problem solved. I can figure out your emotional state because I mimic it. I can understand your gestures because I imagine making the same gestures. Logically, however, this explanation can’t possibly be the whole story. Before Brain A can mirror the state of Brain B, it needs to know what state to mirror. We are left with the same question: how does Brain A know the state of Brain B? Brain A needs a mechanism that generates hypotheses about the state of Brain B.

    Here is how I envision the process. Let’s say you’re happy. I observe you; my visual system processes the image; my area TE and STP (and probably some other brain structures that I will come to in the next chapter) compute properties of your face; my machinery for social perception hypothesizes that you are happy. That machinery then pings my own happiness mechanism. It may be that sending the hypothesis to my happiness mechanism is a way to enhance the hypothesis, to generate a rich set of details, to better capture the associations and implications of happiness. In this way I gain a more nuanced model of the state of your mind. My core machinery for social perception generates the hypothesis; the rest of my brain enhances the hypothesis.

    As another example, suppose I watch John reach out and pick up a penny from the table top. My visual system processes the input, and my biological-motion neurons in area STP become active. But does STP have a complete model of this biological action? Maybe it has computed the general trajectory and purpose of the act, but how can it check the details? STP sends its model, its reconstruction of John’s action, to the motor circuitry. STP says, in effect, “Motor circuitry, since you’re an expert at movement control, run this initial hypothesis through your machinery and send me back the result. How would you do it, if you had to perform this action?” The mirror neurons run the simulation, compute some of the motoric details, and send information back. Now STP has available to it a much more finely nuanced, computationally complete description of John’s act. Not only does STP know that John is reaching out to pick up a penny, but the particular shape of his hand is explainable. The particular way he flattens his fingers, slides the penny to the edge of the table, and pinches it between finger and thumb as it slides off the edge, all of these nuances become available. By recruiting the expertise of motor circuitry, STP gains computational power, and I gain a perceptual model of John’s behavior that is all the more detailed and accurate. The mirroring, the use of my motor system to mentally imitate, is a tool that is used to help enrich and refine my understanding of John’s action.

    Like a spider at the center of a web, the core circuitry for social perception (perhaps mainly STP, perhaps including other brain areas) generates hypotheses and sends pings to the rest of the brain—to the motor brain, to the memory brain, to the emotional brain, to the vocal brain—receives feedback, asks whether this or that computed