Beyond the Cartesian Theater: How Indiana University Research Challenges the Linear Model of Human Decision-Making

For generations, the standard psychological and neuroscientific account of human behavior has relied on a neat, sequential narrative. A sensory stimulus is perceived by the eyes or ears, evaluated by a central cognitive processor, and finally converted into physical action by the motor system. This linear framework, often casually referred to by cognitive scientists as the sandwich model—with sensation and action forming the bread, and a distinct cognitive decision-making phase trapped in the middle—has dictated both experimental design and everyday intuition.

However, a provocative new paper published in the Journal of Cognitive Neuroscience by Tom James, a professor in the Department of Psychological and Brain Sciences at Indiana University, challenges this foundational assumption. According to James’s research and theoretical framework, detailed in his article Sensorimotor Mechanisms of Decisions and Actions, the conscious experience of making a deliberate choice bears little resemblance to the actual, distributed neural processes unfolding inside the brain. Instead of a centralized executive committee issuing commands, human behavior emerges from a continuous, simultaneous interplay among the brain, the body, and the external environment.

This theoretical pivot promises to disrupt traditional cognitive neuroscience. By questioning the very existence of a central neural controller, James’s work invites the scientific community to reconsider decades of model-based research and adopt more complex, embodied approaches to understanding how humans navigate the world.

The Evolution of the Sandwich Model and the Linear Fallacy

The historical roots of the linear decision-making model run deep, drawing from early philosophical traditions that sharply divided the mind from the body. As early as the 17th century, thinkers like René Descartes grappled with how a nonphysical mind could interact with a physical machine like the human body, planting the seeds for what modern philosophers call the "Cartesian Theater"—the illusion that a homunculus, or a tiny person, sits inside the control room of the brain, watching the sensory screens and pulling the levers of action.

Throughout the 20th century, the rise of computer science and cognitive psychology heavily reinforced this serial processing paradigm. Early computational models of the mind treated the brain like a digital computer: input enters the system, software algorithms process the data, and an output is generated. Model-based cognitive neuroscience built entire subfields around this assumption, attempting to isolate distinct neural correlates for perception, valuation, and motor execution.

From an introspective standpoint, this model feels undeniably correct. When an individual decides to reach for a cup of coffee, it feels as though a conscious desire initiates a thought, which then causes the arm to move. As James observes, our actions undeniably feel like they are caused by decisions rooted in our beliefs, desires, and intentions.

Yet, James argues that this subjective experience is an abstract description rather than a mechanistic explanation. While sensory systems have identifiable neural mechanisms and motor systems have clear physiological pathways, the supposed cognitive stage in between lacks a corresponding, dedicated neural organ. There is no isolated cluster of neurons whose sole function is to act as the ultimate decision-maker.

Physicalism, Abstract Descriptions, and the Danger of the Infinite Regress

To build his critique, James adopts a rigorous physicalist framework, heavily influenced by the philosophical writings of Daniel Dennett. Physicalism posits that physical phenomena can cause both physical and nonphysical outcomes, but nonphysical phenomena—such as abstract thoughts, desires, or purely mental decisions—cannot independently exert a physical force on the material world.

If decisions are categorized as nonphysical mental phenomena defined at a high level of abstraction, they cannot literally trigger physical muscle contractions. To clarify this paradox, James relies on powerful analogies, starting with Dennett’s famous comparison between the self and an object’s center of mass (CoM).

A center of mass is an indispensable mathematical tool in physics and engineering. It allows scientists to calculate trajectories, stability, and balance with remarkable accuracy. However, a center of mass is an abstract description, not a physical object; one cannot reach out and physically touch an object’s center of mass independently of the object itself. Furthermore, the center of mass does not exert a physical force to move the object; rather, the physical distribution of mass dictates both the movement and the resulting location of the center of mass.

James applies the exact same logic to human decisions. Saying that a person made a financial investment because of a "decision" is a wonderfully efficient way to summarize complex behavior, but it tells us nothing about the actual neurological mechanisms at play.

He offers a second institutional analogy: the use of the term "the university." When media outlets report that "the university took certain disciplinary actions during a campus protest," the phrase conveniently encapsulates the collective behavior of thousands of individuals, buildings, bureaucratic policies, and institutional histories. Yet, a truly granular explanation of the event requires examining specific phone calls between administrators, meetings with campus security, and individual student protests.

Similarly, invoking "decisions" provides a high-level summary of human behavior while completely obscuring the micro-level neurological events occurring across distributed brain networks. As James succinctly puts it, mental phenomena are simply defined on too abstract a level to satisfy the rigorous explanatory goals of modern cognitive neuroscience.

Furthermore, retaining the concept of a central controller invites an intractable philosophical trap. If scientists argue that a higher-level executive module inside the brain observes sensory data and issues commands, they immediately face an infinite regress. Who or what is operating the controller? If the answer is a smaller sub-controller, logic demands yet another entity inside that one. As Dennett noted regarding the Cartesian Theater, this approach fails to solve the mystery of consciousness and agency; it merely pushes the unsolved problem one layer deeper.

The Wall-Following Robot: Intentionality Without Intent

To demonstrate how complex, goal-directed behavior can emerge completely free of centralized decision-making, James points to a classic thought experiment in robotics: the simple wall-following robot.

Constructed from a minimal arrangement of basic sensory, motor, and sensorimotor modules, this rudimentary machine possesses no central computer running complex decision algorithms, no strategic database, and no internal representations of goals or intentions. Placed in a room, it simply senses obstacles in its immediate vicinity and reacts according to hardwired feedback loops.

When observed from the outside, however, the robot’s behavior appears remarkably purposeful. It navigates corners smoothly, avoids collisions, and persistently tracks the perimeter of the room. To an untrained observer, it looks strategic, intentional, and thoughtful—as though the machine is constantly making deliberate choices.

Yet, we know with absolute certainty that no decisions are being made inside the machine. The appearance of intention is entirely an emergent property resulting from the robot’s physical interactions with its immediate environment.

This robotic example forces a profound question for behavioral science: If a simple machine can generate convincing, goal-directed behavior without a centralized decision-making apparatus, why must we assume that human beings require a high-level central controller to achieve the same feat? James argues that eliminating the central controller offers a far more parsimonious—and scientifically defensible—explanation of human neurobiology.

Action Selection and the Paradigm Shift in Neuroscience

Rather than framing the brain as a hierarchical command-and-control center, James proposes that behavior is driven by "action selection." In this view, perception and action are not separated by a mysterious cognitive chasm; instead, sensory, sensorimotor, and motor processes operate concurrently, feeding back into one another in real-time loops that span the brain, the body, and the surrounding environment.

This perspective aligns closely with emerging movements in cognitive science, such as embodied cognition and ecological psychology, which argue that the mind cannot be fully understood by studying the brain in a vacuum. Instead, cognition is deeply shaped by the physical body’s morphology and its continuous physical engagement with the world.

Transitioning toward this decentralized framework will not be without its challenges. For decades, standard neuroimaging paradigms and experimental designs have relied on linear models—presenting discrete stimuli, measuring delayed neural responses, and mapping them to distinct behavioral choices.

To capture the complex, non-linear, and simultaneous interactions theorized by James, researchers will need to develop innovative experimental methodologies. This may include hyperscanning techniques, continuous real-time behavioral tracking, and advanced computational models capable of analyzing distributed neural dynamics rather than isolated localized activations.

Broader Implications for Mental Health and Cognitive Science

While James’s paper focuses primarily on basic sensorimotor mechanisms and decision theory, the broader implications of his physicalist, decentralized framework extend far beyond academic philosophy.

Traditional psychiatry and clinical psychology have long relied on diagnostic frameworks that treat mental disorders as dysfunctions of specific cognitive components or internal control systems—such as a "defective executive functioning module" in conditions like ADHD, addiction, or obsessive-compulsive disorder. If James’s perspective gains traction, it could shift clinical paradigms toward viewing mental health conditions as breakdowns in dynamic, distributed sensorimotor loops involving the entire organism and its environment.

Furthermore, artificial intelligence and robotics research stand to benefit immensely from abandoning the search for centralized decision-making architectures. Developing autonomous systems that rely on decentralized, embodied action selection rather than heavy, top-down computational planning could lead to more adaptive, resilient, and life-like artificial agents.

Ultimately, James does not deny the utility of the word "decision." We will undoubtedly continue to use mentalistic language to describe our daily lives, and doing so remains a highly effective way to navigate human social interactions. The scientific leap, however, lies in confusing our useful linguistic descriptions with actual neurobiological architecture. By stripping away the illusion of the Cartesian Theater, cognitive neuroscience may finally begin to chart the true, beautifully complex mechanics of human agency.