For decades, the standard narrative regarding the human brain has been one of sequential efficiency: we perceive the world, we deliberate on that information, and finally, we execute an action. It is a model that feels intuitively correct, mirroring our personal experience of weighing desires, beliefs, and intentions before choosing a path. However, according to Tom James, a professor in the Department of Psychological and Brain Sciences at Indiana University, this “sandwich model” of decision-making—moving neatly from sensory processing to cognition and then to motor activity—may be fundamentally flawed.
In a new paper titled "Sensorimotor Mechanisms of Decisions and Actions," published in the Journal of Cognitive Neuroscience, James argues that the brain does not actually contain a dedicated "decision-making" center. Instead, he suggests that what we perceive as a high-level choice is actually an emergent property of simultaneous, interacting sensory and motor processes.
Rethinking the Brain’s Decision-Making Process
The traditional framework, often utilized in model-based cognitive neuroscience, posits that the brain operates in a linear fashion. In this view, sensation serves as the input, cognition serves as the processor, and motor activity acts as the output. James notes that this structure is deeply ingrained not just in scientific theory, but in the human psyche. "Our actions feel like they are caused by decisions based on desires, beliefs, and intentions," he observes.
However, James contends that this explanation fails to reconcile with our biological understanding of the brain. While scientists have successfully mapped identifiable sensory and motor mechanisms, they have yet to find a corresponding neural structure that functions as a distinct, centralized "decision-maker."
Rather than a singular executive system directing behavior, James proposes a model of "action selection." In this framework, behavior is the product of continuous, dynamic interactions among the brain, the body, and the surrounding environment. These processes do not wait in a queue; they occur simultaneously, constantly feeding back into one another in a complex web that produces the outward appearance of a deliberate choice.
Crucially, James is not suggesting that decisions are "unreal" in a social or behavioral sense. "Of course they do [exist]," he says. "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."
Decisions as Abstract Descriptions
To bridge the gap between our internal experience and the physical reality of neural activity, James employs a "physicalist" framework, a philosophical approach championed by thinkers like Daniel Dennett. The core assumption here is that physical phenomena are the only drivers of physical events. Because sensory and motor processes are physical, and decisions—as mental phenomena—are abstract, James argues that a decision cannot, in a literal, mechanical sense, cause a physical action.
To clarify this distinction, James draws an analogy to the "center of mass" in physics. A center of mass is a vital mathematical concept that helps us understand the movement of objects, but it is not a physical force unto itself. You cannot move the center of mass of an object without moving the object itself; the center is a description of the whole, not a separate entity exerting influence. Similarly, James suggests that a "decision" is an abstract, high-level description of an action, rather than an entity located within the brain that initiates that action.
He further illustrates this using the concept of an institution, such as a university. When we say "the university took action during a protest," we are using a convenient, high-level term to describe a complex, decentralized series of events involving administrators, campus security, and students. However, if a researcher wanted to understand the protest at a granular level, they would need to study the specific phone calls, meetings, and individual movements of those involved. Looking at the "university" as a single decision-making entity tells us nothing about the underlying mechanisms.
According to James, cognitive neuroscience faces a similar hurdle. By focusing on "decisions" as the primary unit of study, researchers are defining phenomena at a level that is too abstract to reveal how the brain actually functions. "As mental phenomena, they are defined on too abstract a level for the goals of cognitive neuroscience," he explains. Simply labeling an act as a "decision" obscures the underlying neural reality.
A Simple Robot Raises a Bigger Question
To challenge the necessity of a central controller, James points to the simplicity of basic robotics. Imagine a machine equipped with a handful of sensory and motor modules programmed to follow a wall. To an outside observer, the robot’s behavior appears highly intentional; it seems to have a strategy, a goal, and perhaps even a plan. Yet, the robot possesses no internal system dedicated to decision-making.
"The robot does not have decisions built into it," James notes. "It just senses its environment and moves around accordingly. And based on the environment, wall-following turns out to be a good thing. It looks intentional. It looks strategic. It looks like the robot is making decisions. And yet, it is not. The reason we know it is not is that there are no systems built into it to do that."
This observation leads to a provocative inquiry: If a rudimentary machine can simulate goal-directed behavior without a central controller, why do we assume the human brain requires one? James argues that his model is significantly more parsimonious—meaning it requires fewer complex, unproven assumptions—than the theory that the brain houses a higher-level regulator.
The Problem With a Central Controller
The reliance on a "central controller" also leads to a classic philosophical trap, often referred to as the "Cartesian Theater." If we suggest there is a higher-level entity inside the brain monitoring information and making choices, we are effectively placing a "person" inside the brain to do the thinking. This leads to an infinite regress: if that internal person is making decisions, who is making decisions inside their brain?
"Explaining that the brain works by way of a central controller suggests that you haven’t figured out how the brain works, because you’ve just put a person inside your brain," says James. "Dennett called this idea the Cartesian Theater. That person inside your brain would need another person inside its brain, which would need a person inside its brain and so on, in an infinite regress. So the problem is never solved. It’s just passed on."
By abandoning the hunt for a central controller, James argues that researchers can pivot toward a more productive focus: the actual, observable interaction between sensory and motor systems.
An Experimental Path Forward
The shift toward viewing decision-making as an emergent property of continuous interactions presents a significant methodological challenge. Current research models, which often rely on linear, step-by-step frameworks, are not necessarily designed to capture the complexity of simultaneous, multi-directional neural processes.
However, James views this not as a roadblock, but as an opportunity for the field. His laboratory has already begun incorporating ideas from "embodied cognition" and "ecological psychology"—disciplines that emphasize the relationship between the mind and the physical world—to explore these dynamics.
The goal is to develop experimental methods capable of mapping how sensory and motor systems influence one another in real-time as an individual interacts with their environment. James believes this approach will eventually allow cognitive neuroscience to move past the "sandwich model" and uncover the true mechanisms that give rise to the behaviors we call decisions. Ultimately, this framework may provide a new lens through which to investigate a wide range of mental phenomena that have long been categorized as distinct, sequestered processes within the brain, potentially transforming our understanding of what it means to choose.
