TOKYO —

Indiana University Professor Tom James is challenging long-held assumptions about how the human brain makes decisions, suggesting that our subjective experience of decision-making may be fundamentally different from the intricate, interconnected processes occurring within our neural architecture. For decades, both scientific inquiry and common intuition have favored a sequential model: perception, followed by thought and choice, culminating in action. This "sandwich model" posits distinct brain functions for each stage, moving from sensory input to cognitive processing and finally to motor output. This linear framework has been a cornerstone for many cognitive neuroscience approaches, including model-based research, and aligns with our internal feeling of making choices based on desires, beliefs, and intentions. However, Professor James argues that this familiar narrative, while intuitively appealing and useful for describing behavior, does not accurately reflect the brain’s underlying mechanisms.

The "Sandwich Model" Under Scrutiny

James’s central argument, presented in his recent publication "Sensorimotor Mechanisms of Decisions and Actions" in the Journal of Cognitive Neuroscience, posits that there isn’t a distinct, centralized "decision-making" module in the brain that acts as a go-between for sensory input and motor output. While sensory processing and motor execution have identifiable neural correlates, the proposed cognitive stage between them lacks a corresponding, singular neural process that functions as a dedicated decision-maker.

Instead, James proposes that what we perceive as decision-making is, in fact, a product of "action selection" emerging from the dynamic and simultaneous interactions of sensory, sensorimotor, and motor processes. This perspective views behavior not as a linear progression, but as an emergent property of ongoing feedback loops between the brain, the body, and the environment. These processes, he contends, can and do occur concurrently, influencing each other in real-time rather than unfolding in a strictly sequential manner.

A Physicalist Framework for Understanding Mind

To ground his argument, Professor James employs a "physicalist" framework, drawing inspiration from philosophers such as Daniel Dennett. This philosophical stance asserts that physical phenomena can be the cause of both physical and nonphysical phenomena, but crucially, nonphysical phenomena cannot independently cause physical events. Within this framework, sensory and motor processes are undeniably physical. Decisions, however, are considered nonphysical or abstract descriptions. If this is the case, James reasons, a nonphysical decision cannot directly cause a physical action.

This leads to a re-evaluation of how we conceptualize decisions in relation to brain activity. James suggests that decisions, much like abstract concepts in science, serve as useful descriptions rather than direct causal agents.

Analogy of the Center of Mass and Abstract Concepts

To illustrate his point, James draws upon Daniel Dennett’s analogy of the "center of mass." A center of mass is a powerful mathematical concept that simplifies our understanding of an object’s behavior, but it 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 proposes that a decision might be an abstract description of a behavioral outcome rather than a distinct physical entity within the brain that initiates action.

Another analogy highlights how useful high-level descriptions can become less informative when examining phenomena at a more granular level. Consider the term "the university." This phrase efficiently encapsulates a complex web of people, buildings, departments, and processes. However, stating that "the university took action during a campus protest" offers little insight into the specific physical events involved. A more detailed explanation would necessitate examining individual actions like meetings between administrators, phone calls to law enforcement, or specific departmental responses. James argues that "decisions" function similarly for neuroscience, providing a convenient, abstract label for behavior without revealing the intricate physical mechanisms that produce it. As he states, "As mental phenomena, they are defined on too abstract a level for the goals of cognitive neuroscience." Simply stating that a decision was made does not explain the underlying neural activity.

The Robot Analogy: Intentionality Without a Decision Maker

Pushing his argument further, James introduces a third example: a simple robot designed with minimal sensory, motor, and sensorimotor modules. This robot can exhibit "wall-following" behavior, which, from an external perspective, can appear purposeful, strategic, and even intentional. However, this robot possesses no internal system 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 profound question: if a relatively simple machine can generate behavior that appears intentional without an explicit decision-making system, could human behavior also be the result of complex interactions that mimic centralized decision-making, even in the absence of such a singular process? James suggests that this explanation is more parsimonious than assuming the existence of a "higher-level, central controller that monitors and regulates sensory and motor processes."

The Philosophical Quagmire of the "Central Controller"

The concept of a central controller, an internal entity responsible for observing information and dictating actions, faces a significant philosophical hurdle, one that has been debated since the time of René Descartes. If such a controller exists within the brain, the question then arises: how does that controller operate?

"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," James notes. He refers to this as the "Cartesian Theater." This anthropomorphic approach leads to an infinite regress: the internal controller would require its own controller, which would require another, and so on, perpetually deferring the explanation of how decisions are truly made. Instead of invoking such an internal decision-maker, James advocates for a direct focus on the interacting sensory and motor systems that actively generate behavior.

Methodological Shifts for a New Understanding

If decision-making is indeed an emergent property of continuous interactions among the brain, body, and environment, then studying it necessitates experimental methodologies that can capture this dynamic complexity. Professor James acknowledges that this presents both exciting opportunities and considerable methodological challenges for cognitive neuroscience. Researchers will need to move beyond purely linear models and investigate processes that occur simultaneously, influence one another, and evolve dynamically as an individual interacts with their surroundings.

James’s own laboratory is already embarking on this path, drawing on theoretical frameworks from embodied cognition and ecological psychology. This approach aims to capture the reciprocal influences between an organism and its environment in real-time. By examining how sensory information is integrated with motor planning and execution in a continuous feedback loop, researchers can begin to understand the mechanisms that give rise to what we colloquially term "decision-making."

Broader Implications for Cognitive Science

The implications of Professor James’s work extend beyond the study of decision-making. This shift in perspective could offer new avenues for investigating a wide array of cognitive and mental phenomena that have traditionally been treated as discrete, internally processed functions. By viewing these phenomena as emergent properties of interconnected physical systems interacting with their environment, cognitive neuroscience may unlock a more unified and accurate understanding of the human mind. This paradigm shift promises to reshape how we conceptualize and empirically investigate the very nature of thought, perception, and action. The research is anticipated to catalyze further investigation into how complex behaviors, which we often attribute to conscious deliberation, can arise from the intricate interplay of simpler, interconnected neural and bodily processes.