TOKYO —

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 sequential process: perception, cognition, and then action. This linear framework, often referred to as the "sandwich model," has underpinned much of cognitive neuroscience. However, Professor James, in his recent publication in the Journal of Cognitive Neuroscience, argues for a fundamental reevaluation of this long-held understanding, proposing that behavior emerges from dynamic, simultaneous interactions rather than a discrete cognitive decision-making stage.

The Conventional "Sandwich Model" Under Scrutiny

The traditional view of decision-making posits a clear progression. Sensory input is received, processed by cognitive faculties to form beliefs, desires, and intentions, which then culminate in a deliberate choice, ultimately leading to motor output. This model aligns with our subjective experience – actions feel like the direct consequence of internal deliberations. Scientific approaches, particularly model-based cognitive neuroscience, have largely adopted this sequential, modular framework, attributing distinct brain functions to each stage: sensory processing, cognitive deliberation, and motor execution.

Professor James challenges this established paradigm by highlighting a critical disconnect: while distinct neural mechanisms for sensation and action are well-documented, a clearly defined, independent neural process that functions solely as a "decision maker" between perception and action has remained elusive. This absence, he argues, suggests that the "sandwich model" may be an oversimplification, failing to capture the intricate reality of neural activity.

Action Selection: A New Framework for Understanding Behavior

Instead of a dedicated decision-making module, James proposes that what we perceive as decisions are, in fact, the emergent outcome of "action selection." This concept posits that behavior arises from the continuous, interconnected interplay of sensory, sensorimotor, and motor processes. These processes do not necessarily unfold in a strict sequence but can operate concurrently, influencing and feeding back into one another in a dynamic loop. This perspective shifts the focus from a central executive controller to the distributed, interactive nature of neural systems.

"Our actions feel like they are caused by decisions based on desires, beliefs, and intentions," James acknowledges, validating the intuitive appeal of the traditional model. "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." This statement encapsulates the core of his argument: while the description of behavior as decision-driven is useful, the underlying mechanism may not involve a distinct decision-making entity.

The Philosophical Underpinnings: Physicalism and the Nature of Decisions

Professor James’s argument is grounded in a "physicalist" philosophical framework, drawing inspiration from thinkers like Daniel Dennett. Physicalism posits that all phenomena, including mental ones, are ultimately physical in nature or are caused by physical processes. Crucially, in this framework, physical phenomena can cause both physical and nonphysical phenomena, but nonphysical phenomena cannot independently cause physical events.

Applying this to decision-making, James posits that sensory and motor processes are inherently physical. If decisions are considered nonphysical mental phenomena, then, according to strict physicalism, a nonphysical decision cannot directly cause a physical action. This leads to a re-examination of how we conceptualize the causal link between our internal states and external behaviors.

Analogies Illuminating Abstract Concepts

To make his complex argument more accessible, Professor James employs several illuminating analogies. One of the most compelling draws from Daniel Dennett’s comparison of the "self" to a "center of mass" (CoM) or "center of gravity." A center of mass is a powerful mathematical concept used to describe the distribution of mass in an object. It is incredibly useful for calculations and predictions about how an object will behave under external forces. However, the center of mass itself is not a physical entity that can exert force independently. You cannot move an object’s center of mass without moving the object itself.

Similarly, James suggests that a "decision" might function as an abstract description, a conceptual tool for understanding and predicting behavior at a higher level, rather than a discrete physical entity within the brain that directly initiates action. It’s a useful label we apply to a complex set of underlying physical processes, but it doesn’t possess independent causal power in the physical realm.

Another analogy highlights how high-level descriptions can become less informative when examining finer-grained mechanisms. Consider the term "the university." This single phrase effectively encapsulates a vast collection of people, buildings, departments, and intricate processes. When we say, "the university took certain actions during a campus protest," this statement provides a convenient, albeit abstract, summary. However, to understand the specifics of what occurred, one would need to delve into the detailed actions of administrators, police communications, student organizing efforts, and other granular events.

James argues that "decisions" function in a similar manner for neuroscience. While the concept of a decision is invaluable for describing behavior at a macroscopic level, it offers limited insight into the precise neural mechanisms that generate that behavior. As James maintains, "As mental phenomena, they are defined on too abstract a level for the goals of cognitive neuroscience." In essence, stating that an individual "made a decision" doesn’t explain the underlying physical processes in the brain that led to the observed action.

The Robot’s Dilemma: Intentionality Without a Decision Maker

Further bolstering his argument, Professor James introduces the example of a simple robot designed to exhibit "wall-following" behavior. This robot, constructed from a limited array of sensory, motor, and sensorimotor modules, can navigate its environment in a way that appears purposeful. From an external observer’s perspective, the robot might seem to possess goals, strategies, and even intentions.

However, this robot has no internal system specifically designed for decision-making. It operates solely on direct sensory input and corresponding motor responses. Its "wall-following" behavior is a natural consequence of its physical design and its interaction with the environment. The perceived intentionality and strategic nature of its actions arise from the emergent properties of its simple, interconnected systems.

"The robot does not have decisions built into it," James explains. "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 question: If a relatively simple machine can produce behavior that appears intentional without an explicit decision-making system, could human behavior similarly appear to be driven by centralized decisions, even if no such central process exists in the brain? James posits that this explanation is more parsimonious – requiring fewer assumptions – than positing a complex, "higher-level, central controller that monitors and regulates sensory and motor processes."

The "Cartesian Theater" Problem: An Infinite Regress

The concept of a central controller within the brain raises significant philosophical challenges, dating back to René Descartes. If some internal entity is responsible for observing information and making decisions, then the question arises: how does that controller itself work? This leads to what philosopher Daniel Dennett termed the "Cartesian Theater" problem.

The "Cartesian Theater" is the idea that there must be a central place in the brain where all sensory information converges, and from which conscious awareness and decisions emanate, akin to a stage in a theater where an audience (the conscious self) watches the play of sensory input. However, if a central controller exists, then that controller itself would presumably need its own internal observer and decision-maker to function, leading to an infinite regress. As James puts it, "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." This recursive problem means the ultimate mechanism of control remains unexplained, simply being deferred to an ever-deeper layer.

By advocating for a focus on the interacting sensory and motor systems that directly generate behavior, James seeks to circumvent this problematic infinite regress and offer a more scientifically grounded explanation.

An Experimental Path Forward: Embracing Complexity

If decision-making is not a discrete cognitive event but rather an emergent property of continuous interactions among the brain, body, and environment, then studying it requires a shift in experimental methodology. Traditional linear models, which examine processes in isolation or in strict sequence, may be insufficient. Researchers must develop and employ methods capable of capturing the dynamic, simultaneous, and feedback-rich nature of neural activity.

Professor James acknowledges that this presents both exciting opportunities and significant methodological challenges. The goal is to move beyond reductionist approaches and embrace the complexity of embodied cognition and ecological psychology, fields that emphasize the interconnectedness of an organism with its environment.

James’s own laboratory is actively exploring this new direction. By integrating principles from these fields, researchers aim to develop experimental paradigms that can capture the real-time, multifaceted interactions that underpin behavior. This could involve techniques that track neural activity while individuals engage in complex tasks within rich, dynamic environments, allowing for the observation of how sensory input, motor output, and internal states continuously influence each other.

The implications of this paradigm shift extend beyond understanding decision-making. This new framework could offer novel insights into a wide array of cognitive and mental phenomena that have traditionally been treated as distinct, internally located processes. By viewing these phenomena as emergent properties of embodied, environmentally situated systems, cognitive neuroscience may unlock deeper and more accurate explanations for phenomena such as learning, memory, and consciousness. This research, published in the Journal of Cognitive Neuroscience, marks a significant step towards a more integrated and dynamic understanding of the human mind and its intricate relationship with the world.