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.