TOKYO —

Indiana University Professor Tom James is challenging long-held assumptions about how the human brain makes decisions, proposing a radical departure from the conventional "sandwich model" of cognition. For decades, scientific theories and everyday intuition have depicted decision-making as a linear sequence: perceive, think, choose, and act. This familiar narrative, where distinct brain functions neatly align with each stage—sensory processing, cognition, and motor activity—is deeply ingrained in cognitive neuroscience and aligns with our subjective experience of conscious deliberation. However, Professor James’s groundbreaking research, published in the Journal of Cognitive Neuroscience, suggests this sequential framework is an oversimplification, failing to accurately reflect the complex, interconnected neural processes at play.

The Conventional "Sandwich Model" Under Scrutiny

The prevailing understanding of decision-making has largely operated under a sequential paradigm. This model posits that external stimuli are first received by sensory systems, then processed by cognitive centers for deliberation and choice, and finally translated into motor commands for action. This linear progression is not only intuitive but also forms the bedrock of many established scientific models. As Professor James himself notes, "Our actions feel like they are caused by decisions based on desires, beliefs, and intentions." This subjective feeling of agency, of a conscious self weighing options and issuing commands, has historically guided scientific inquiry.

However, Professor James argues that this widely accepted "sandwich model" struggles to align with empirical findings about brain function. While identifiable neural mechanisms exist for sensory input and motor output, the proposed cognitive stage—the supposed nexus of decision-making—lacks a distinct, identifiable neural process that functions as a singular "decision maker." Instead, James proposes a more integrated view, where what we perceive as decision-making is, in fact, a product of continuous, dynamic interactions among sensory, sensorimotor, and motor processes, collectively leading to "action selection." This perspective suggests that behavior emerges not from a top-down command structure but from the ongoing interplay between the brain, the body, and its environment, with these processes occurring simultaneously and influencing each other in a feedback loop.

The Philosophical Underpinnings: Physicalism and Abstract Descriptions

Professor James’s argument is rooted in a "physicalist" framework, a philosophical stance that posits that all phenomena are ultimately physical. This approach, influenced by thinkers like Daniel Dennett, asserts that physical phenomena can cause both physical and nonphysical events, but nonphysical phenomena, by themselves, cannot directly cause physical events. In this context, sensory and motor processes are undeniably physical. Decisions, however, are often conceptualized as nonphysical mental events.

If decisions are considered nonphysical, James contends, then they cannot, in a literal sense, be the direct physical cause of an action. This leads to a crucial distinction: decisions might serve as useful conceptual tools for describing behavior at a higher level, but they may not represent the underlying physical mechanisms that produce that behavior.

Analogies Illuminating the Concept

To elucidate this complex idea, Professor James employs several illuminating analogies.

Decisions as Abstract Descriptions, Not Causal Agents

One compelling analogy 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 that simplifies the description of an object’s physical properties. However, a center of mass is not a physical entity that can independently exert force or initiate movement. You cannot move an object’s center of mass without moving the object itself. Similarly, James proposes that a decision might function as an abstract description—a convenient label for a complex set of underlying physical processes—rather than a discrete physical entity that directly triggers an action.

Another analogy highlights how abstract concepts, while useful for everyday communication, can become less informative when seeking detailed scientific understanding. Consider the term "the university." This phrase effectively encapsulates a vast network of people, buildings, departments, and intricate processes. Saying "the university took action during a campus protest" is a common and understandable statement. However, from a scientific perspective, it offers little insight into the specific events that transpired. A more precise explanation would involve detailing meetings between administrators, phone calls to law enforcement, and the individual actions of various stakeholders.

Professor James argues that "decisions" present a similar challenge for neuroscience. While they provide a useful high-level description of observable behavior, they may obscure the granular physical mechanisms that generate that behavior. As James emphasizes, "As mental phenomena, they are defined on too abstract a level for the goals of cognitive neuroscience." In essence, stating that someone "made a decision" does not, by itself, explain the intricate neural activity that underlies that behavior.

The Robot Analogy: Intentionality Without a Decision Maker

To further press his argument, James introduces a third illustrative example: a simple robot designed with basic sensory, motor, and sensorimotor modules. This robot can exhibit "wall-following" behavior, which, from an external perspective, can appear to be driven by purpose, strategy, and even intention. The robot senses its environment and moves accordingly. When confronted with a wall, its programming dictates a response that results in it following the wall. This behavior can be interpreted as goal-directed, as if the robot is actively making decisions to navigate its surroundings.

However, critically, this robot lacks any internal system explicitly designed for decision-making. "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 and strategic without possessing a dedicated decision-making system, could human behavior also manifest in ways that seem to result from centralized decisions, even if no such central process exists in the brain? Professor James suggests this explanation is more parsimonious—more economical and less reliant on complex, unproven mechanisms—than positing the existence of a "higher-level, central controller that monitors and regulates sensory and motor processes."

The Problem of the "Cartesian Theater"

The concept of a central controller, an internal decision-maker that orchestrates behavior, also runs into significant philosophical hurdles, dating back to René Descartes. If a higher-level entity within the brain is responsible for processing information and making choices, the fundamental question remains: how does that controller itself function?

Professor James articulates this dilemma succinctly: "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 is the essence of what philosopher Daniel Dennett termed the "Cartesian Theater"—the idea of an internal observer or decision-maker within the mind. The problem with this concept is that it leads to an infinite regress. If this internal controller makes decisions, it too would require its own internal controller to make its decisions, and so on, ad infinitum. The problem of explanation is merely passed on, never truly solved.

Instead of invoking such an elusive internal decision-maker, James advocates for a shift in focus: studying the directly observable, interacting sensory and motor systems that demonstrably generate behavior.

An Experimental Path Forward: Embracing Complexity

If decision-making, as we perceive it, emerges from the continuous, dynamic interactions among the brain, body, and environment, then studying it requires experimental methodologies capable of capturing this inherent complexity. Professor James acknowledges that this presents both exciting research opportunities and significant methodological challenges. Researchers will need to move beyond strictly linear models and develop ways to examine processes that occur simultaneously, exert mutual influence, and adapt as an individual interacts dynamically with their surroundings.

Professor James’s own laboratory is actively exploring this new direction, drawing inspiration from fields such as embodied cognition and ecological psychology. These approaches emphasize the inseparable link between an organism’s physical form, its environment, and its cognitive processes. By integrating insights from these areas, researchers can begin to unravel the intricate mechanisms that give rise to behaviors we conventionally label as "decision-making." This paradigm shift holds the potential not only to illuminate the nature of decisions but also to offer novel avenues for investigating a wide array of other cognitive and mental phenomena that have traditionally been compartmentalized as distinct internal brain processes. The implications of this research extend far beyond the study of choice, potentially reshaping our fundamental understanding of how the mind and brain interact to produce the rich tapestry of human experience and behavior.