Your Brain May Not Actually 'Decide' Anything, Neuroscientist Argues

What we experience when making a decision may be very different from what actually happens inside the brain, according to Indiana University professor Tom James. For decades, both scientific theories and everyday intuition have described decision-making as a sequence: we perceive something, think about it, choose, then act. Many approaches in cognitive neuroscience are built around this same linear framework, sometimes called the 'sandwich model.'

James argues this familiar picture does not fit what scientists know about the brain. Sensation has identifiable sensory mechanisms, and action has identifiable motor mechanisms. But the supposed thinking stage in between does not appear to have a matching neural process that acts as a distinct decision-maker. Instead, James proposes that sensory, sensorimotor and motor processes together produce what he calls 'action selection,' with behavior emerging from ongoing, simultaneous interactions among the brain, the body and the environment, not a simple sequence.

James is not saying decisions are unreal. “We use this language all the time and it's very helpful in terms of describing behavior,” he said. But he argues the brain does not need a dedicated decision-making system to produce behavior that merely looks that way. He presents the argument in a paper titled “Sensorimotor Mechanisms of Decisions and Actions,” published in the Journal of Cognitive Neuroscience.

To make the idea concrete, James compares a decision to a center of mass: a useful concept for describing an object, but not something that can itself push the object, since you cannot move a center of mass without moving the whole object. In the same way, he says, a decision may be an abstract description rather than a physical thing that directly causes an action.

James also points to a simple robot built from a small number of sensory, motor and sensorimotor modules, which shows 'wall-following' behavior that looks purposeful, as if it has goals and strategies. “The robot does not have decisions built into it,” James said. “It just senses its environment and moves around accordingly.” If a simple machine can look intentional without any decision-making system, he argues, it is more economical to assume human behavior works the same way than to assume the brain contains a “higher-level, central controller” overseeing sensory and motor processes.