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 handlebar is connected to the front wheel for
steering, the seat is over the pedals to make it easy to push down, the gear
chain connects to the rear wheel to cause it to propel the bike forward, and so
on.
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.
