How the Brain Creates Personality: A New Theory

Are you a mover, a perceiver, a stimulator, or an adapter? Modes of thinking can be understood in terms of how the top and bottom—rather than right and left—parts of the brain interact.
(Wikimedia Commons)

It is possible to examine any object—including a brain—at different levels. Take the example of a building. If we want to know whether the house will have enough space for a family of five, we want to focus on the architectural level; if we want to know how easily it could catch fire, we want to focus on the materials level; and if we want to engineer a product for a brick manufacturer, we focus on molecular structure.

Similarly, if we want to know how the brain gives rise to thoughts, feelings, and behaviors, we want to focus on the bigger picture of how its structure allows it to store and process information—the architecture, as it were. To understand the brain at this level, we don’t have to know everything about the individual connections among brain cells or about any other biochemical process. We use a rela­tively high level of analysis, akin to architecture in buildings, to characterize relatively large parts of the brain.

To explain the Theory of Cognitive Modes, which specifies general ways of thinking that underlie how a person approaches the world and interacts with other people, we need to provide you with a lot of information. We want you to understand where this theory came from—that we didn’t just pull it out of a hat or make it up out of whole cloth. But there’s no need to lose the forest for the trees: there are only three key points that you will really need to keep in mind.

First, the top parts and the bottom parts of the brain have differ­ent functions. The top brain formulates and executes plans (which often involve deciding where to move objects or how to move the body in space), whereas the bottom brain classifies and interprets incoming information about the world. The two halves always work together; most important, the top brain uses information from the bottom brain to formulate its plans (and to reformulate them, as they unfold over time).

Second, according to the theory, people vary in the degree that they tend to rely on each of the two brain systems for functions that are optional (i.e., not dictated by the immediate situation): Some people tend to rely heavily on both brain systems, some rely heavily on the bottom brain system but not the top, some rely heavily on the top but not the bottom, and some don’t rely heavily on either system.

Third, these four scenarios define four basic cognitive modes— general ways of thinking that underlie how a person approaches the world and interacts with other people. According to the Theory of Cognitive Modes, each of us has a particular dominant cognitive mode, which affects how we respond to situations we encounter and how we relate to others. The possible modes are: Mover Mode, Perceiver Mode, Stimulator Mode, and Adaptor Mode.

Systems, Not Dichotomies

We use what researchers have learned to present a new theory of brain function that hinges on how the top and bottom parts of the brain interact. But we do not try to characterize the top and bottom parts of the brain in terms of a simple dichotomy or set of dichotomies, which was exactly what was done with the existing and well-known division of the brain into two halves: namely the left versus the right, the dominant pop-culture brain story of the last few decades. You have probably heard of this theory, in which the left and right halves of the brain are characterized, respectively, as logical versus intuitive, verbal versus perceptual, analytic versus synthetic, and so forth. The trouble is that none of these sweeping generalizations has stood up to careful scientific scrutiny. The dif­ferences between the left and right sides of the brain are nuanced, and simple, sweeping dichotomies do not in fact explain how the two sides function.

When considering large portions of the brain, we need to think about systems—not dichotomies. A system has inputs and outputs, and a set of constituent components that work together to produce appropriate outputs for particular inputs.

A bicycle is a familiar system: The inputs are forces that push down on the pedals, slight movements of the rider’s body made in the act of balancing, and force that moves the handlebars. The components include the seat, the wheels, the handlebars, the pedals, the gears, the chain, and so forth. The outputs are the bike’s forward motion, keeping upright, and going in a specific direction, all at the same time. Crucially, the components are designed to work together to produce appropriate outputs for the system as a whole—for the entire bike.

The same is true of the brain: It has different areas that do dif­ferent things, and the result of the brain areas’ working together is to produce appropriate outputs (such as your avoiding an object) for particular inputs (such as specific sights and sounds). For instance, if you see a car roaring toward you, you jump out of the way.

Top Brain, Bottom Brain

The Theory of Cognitive Modes is based on organizing the brain into two major parts, top and bot­tom—each of which we will characterize as a large system that pro­cesses information in particular ways. As we show, we gain a lot by organizing the brain into these two large systems, noting how con­stituent parts work together. Let’s begin by being clear about what we mean by the top and bottom parts: Look at the diagram of a side view of the brain, which shows the cerebral cortex, the thin outer covering of the brain where most of the bodies of neurons reside. The cerebral cortex is where most cognitive activities arise—and we focus almost entirely on the cerebral cortex (not the “inner brain” structures that are located under the cortex, in the in­terior of the brain, and are involved in emotion and many automatic functions such as controlling arousal and hunger).

[IMAGE DESCRIPTION]
The lobes of the brain. Note that the crease along the top of the temporal lobe is the Sylvian fissure, which divides most of the bottom brain from the top brain. (Simon and Schuster)

The diagram notes the locations of the four lobes of the brain— occipital, temporal, frontal, and parietal—and the location of the Sylvian fissure, a large, highly visible crease that roughly divides the brain into top and bottom parts. Each of the lobes implements many relatively specialized systems, but for our purposes it will be most useful to group the lobes into two large processing systems: The occipital and temporal lobes are in the bottom part of the brain, and the parietal and most of the frontal lobes are in the top part of the brain. A further neuroanatomical distinction must also be made: The frontal lobe itself can be divided into a top and bottom portion, based on how these portions are connected to the parietal and tem­poral lobes, respectively. Thus the brain neatly divides into a top and bottom part.

Presented by

Stephen M. Kosslyn and G. Wayne Miller

Stephen M. Kosslyn, PhD, is the founding dean of the Minerva Schools at the Keck Graduate Institute. He was previously the director of the Center for Advanced Study in the Behavioral Sciences at Stanford University. G. Wayne Miller is a staff writer at The Providence Journal, a documentary filmmaker, and the author of several books.

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