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 tended to describe decision-making as a sequence. First we perceive something, then we think about it and make a choice, and finally we act. Each step is often assumed to correspond to a distinct brain function, moving from sensory processing to cognition and then to motor activity.
Many scientific approaches, particularly model-based cognitive neuroscience, are built around this same linear framework. It also matches how decision making feels from the inside. As James notes, "Our actions feel like they are caused by decisions based on desires, beliefs, and intentions."
Rethinking the Brain's Decision Making Process
James argues that this familiar explanation, sometimes called the "sandwich model," does not fit neatly with what scientists know about the brain. Sensation has identifiable sensory mechanisms, and action has identifiable motor mechanisms. But the supposed cognitive stage between the two does not appear to have a corresponding neural process that functions as a distinct decision maker.
Rather than proposing a dedicated decision-making system that directs behavior, James suggests that sensory, sensorimotor, and motor processes together produce what he calls 'action selection.' In this view, behavior emerges through ongoing interactions among the brain, body, and environment. These processes can occur simultaneously and feed back into one another rather than unfolding as a simple sequence.
That does not mean James believes decisions are unreal.
As James says, "Of course they do. We use this language all the time and it's very helpful in terms of describing behavior. The leap, I think, is to say that the brain works by having decision-making or control processes. It produces behavior that is well described in that way. But it doesn't need a process that does that to make it look that way."
James, a professor in the Department of Psychological and Brain Sciences in the College of Arts and Sciences, presents the argument in "Sensorimotor Mechanisms of Decisions and Actions," an article just published in the Journal of Cognitive Neuroscience.
What Happens in the Brain When We Make a Decision?
James develops his argument using a "physicalist" framework associated with philosophers such as Daniel Dennett. The approach makes explicit what James sees as a basic assumption underlying science: physical phenomena can cause both physical and nonphysical phenomena, while nonphysical phenomena cannot themselves cause physical events.
Sensory and motor processes, for example, are physical. Decisions, in this framework, are nonphysical. If that is the case, James argues, a decision cannot literally cause a physical action.
To make the idea easier to understand, he uses several analogies.
Decisions as Abstract Descriptions
Drawing on Daniel Dennett's comparison between the self and a center of mass (CoM) or center of gravity, James suggests that decisions may function in a similar way. A center of mass is a useful mathematical concept, but it cannot independently exert a physical force. (i.e., you cannot move an object's center of mass without moving the object) In the same sense, James proposes that a decision may be an abstract description rather than a physical entity that directly causes something to happen.
Another analogy shows how useful concepts can become less informative when scientists need to understand events at a more detailed level.
