God Soul Mind Brain

personal space may seem like an esoteric topic—I suppose it is—but I have a special interest in it, having published half a dozen technical reports on it. The brain contains several areas, cortical and subcortical, that seem to play a role in detecting looming stimuli and in controlling defensive behavior such as ducking and flinching. Some of these areas are probably part of basic, essential reflex loops meant to protect the body. I have always thought, however, that the looming-sensitive neurons in STP must play a special role in social interaction. They seem to be especially sensitive to the movement and location of people and animals rather than of inanimate objects.

    Faces, gestures, limb movements, the direction of someone else’s gaze, the looming of nearby bodies—all of these form the raw material for social perception. At some point in the evolution of the brain, the streams for analyzing object motion, object shape, and object location must have fused at the highest level and formed area STP, a specialist in social signals. The particular neuron types that have been discovered so far are presumably only the most obvious, the most easily demonstrated in a monkey. The presumption is that STP must be chock-full of neurons that process the subtleties of social perception.

Social perception and social cognition

    Monkeys and humans are both experts at social perception, and both have the brain area STP that seems to perform some of the necessary computations. (In humans, the cortical area is sometimes called STS. I will call it STP for consistency.) Humans, however, are much better than monkeys at social cognition. Does STP perform social cognition in humans?

    I described social cognition in Chapter 2. A particularly clear example of social cognition is the theory-of-mind task. In that task, you are told a story and asked a question. Sally puts a sandwich in the refrigerator; when she’s not looking, Anne hides it in the freezer; where will Sally look for her sandwich? To answer the question, you must use some basic social cognition. You must analyze the events from Sally’s point of view. As far as she knows, the sandwich is still in the refrigerator, and therefore that is where she will look. Solving this task requires some theorizing about the inside of Sally’s mind.

    When a person is placed in a brain scanner and asked to solve the theory-of-mind task, area STP and some surrounding cortical areas show an elevated activity. In humans, therefore, STP is not solely involved in basic social perception, but is also involved in more complex tasks of social cognition. A possible network of areas involved in social perception and cognition is currently being explored. This network includes STP, a nearby cortical area called TPJ, an area in the front of the brain called the medial prefrontal cortex, and several subcortical structures. Whether these areas are exclusively dedicated to social cognition, or serve a range of other functions, is not yet clear.

    Are these areas, that are involved in social intelligence, also important in creating our own conscious awareness? The following sections describe several hints that this efficiency of function may be the case. The social circuitry—the mechanism that constructs models of other people’s minds, of other people’s awareness and intentions—may indeed double as the circuitry that constructs our own personal perceptions of awareness and intent. This circuitry may lie at the heart of human consciousness.

Conscious and non-conscious vision

    Of all the visual signals that flow through the enormously complex cortical visual system, we are consciously aware of some signals and not others. We are generally conscious of object shape, object motion, and object location. But we are peculiarly unaware of the processing in the action stream. If someone throws a rock at you, for example, you duck reflexively long before you are aware of the rock.

    The view that the action stream is nonconscious, whereas the other visual streams feed into consciousness, was first suggested by Goodale in the 1990s. He studied people who had damage to the visual cortex caused by strokes, carbon monoxide poisoning, or other accidents. (Part of the study of the brain, unfortunately, is a somewhat grim search for people with disabilities.) One patient had no conscious awareness of the shape of objects. She could not report whether an object was a square, a circle, or an oblong,