For generations, both popular perception and established scientific frameworks have largely conceptualized decision-making as a sequential phenomenon. This prevailing model typically posits a progression: an initial sensory input is received, followed by a period of cognitive deliberation leading to a choice, culminating in a subsequent action. Within this paradigm, each stage is often attributed to a discrete neural function, progressing from the processing of external stimuli to internal thought processes and finally to the execution of motor commands. This linear interpretation has profoundly shaped numerous scientific methodologies, particularly within model-based cognitive neuroscience, and it resonates with our subjective experience of agency, where actions feel intrinsically linked to our desires, beliefs, and intentions.
However, a significant re-evaluation of this long-held perspective is being advanced by Professor Tom James of Indiana University. His research suggests that the internal neural events underlying what we experience as decision-making may diverge considerably from this intuitive, sequential interpretation. Professor James contends that the familiar "sandwich model"—which delineates distinct sensory, cognitive, and motor stages—struggles to align with the intricate, dynamic realities of neural processing. While sensory input and motor output possess identifiable neural mechanisms, the hypothesized intermediate cognitive stage, often presumed to be the seat of decision-making, lacks a clearly defined, independent neural process that functions as a singular "decision maker."
Instead of advocating for a specialized, centralized system dedicated to orchestrating behavior, Professor James proposes that what we label as "action selection" emerges from the integrated interplay of sensory, sensorimotor, and motor processes. In this view, behavior is not the product of a deliberate, step-by-step decision but rather a continuous, emergent property arising from the dynamic interactions among the brain, the body, and the surrounding environment. These processes, rather than unfolding in a rigid sequence, can operate concurrently, influencing and feeding back into one another in a complex, ongoing loop.
This does not imply a dismissal of the concept of decisions; rather, it re-frames their role and origin. As Professor James articulates, the language of decisions remains invaluable for describing and understanding behavior in everyday contexts. The crucial distinction, he argues, lies in the leap from using decision-making as a descriptive tool to positing its existence as a direct causal agent or a distinct executive process within the brain. The brain can generate behavior that is readily characterized by decision-making language without necessarily possessing a dedicated internal mechanism that performs this specific function. This perspective is detailed in his recent publication, "Sensorimotor Mechanisms of Decisions and Actions," appearing in the Journal of Cognitive Neuroscience.
Professor James’s argument is grounded in a "physicalist" philosophical framework, drawing inspiration from thinkers like Daniel Dennett. This approach emphasizes the primacy of physical phenomena as causal agents, positing that physical events can give rise to both physical and non-physical outcomes, while non-physical entities, by themselves, cannot directly instigate physical events. Within this framework, sensory and motor processes are inherently physical. If decisions are considered non-physical phenomena, then it follows that they cannot, in a literal sense, directly cause a physical action.
To elucidate this complex idea, Professor James employs several illustrative analogies. One compelling comparison, inspired by Daniel Dennett, likens the concept of a "decision" to a "center of mass" (CoM) or "center of gravity." A center of mass is a highly useful mathematical abstraction that simplifies calculations and predictions about an object’s behavior. However, it is not a physical entity that can independently exert force; one cannot move an object’s center of mass without simultaneously moving the object itself. Similarly, Professor James suggests that a decision might function as an abstract descriptor of a behavioral outcome rather than a tangible, physical entity directly responsible for initiating an action.
Another analogy highlights how abstract concepts, while useful at a macroscopic level, can become less informative when scientific inquiry delves into finer-grained physical mechanisms. Consider the term "university." This is a convenient shorthand, representing a complex aggregation of individuals, buildings, departments, and intricate processes. When we state that "the university took certain actions during a campus protest," this statement provides a high-level summary but offers little insight into the specific physical events involved. A more detailed scientific explanation would necessitate examining the individual actions of administrators, the content of phone calls to law enforcement, and the decisions made by various constituent groups. Professor James contends that "decisions" present a comparable challenge for neuroscience. They may offer a pragmatic, overarching description of behavior but obscure the underlying physical mechanisms that produce it. As he notes, mental phenomena described at such an abstract level are often too generalized for the specific aims of cognitive neuroscience, which seeks to uncover the precise neural underpinnings of behavior. In essence, merely stating that a decision was made does not explain the actual neural events that transpired.
To further illustrate this point, Professor James draws attention to a deceptively simple robot. This machine, constructed from a limited array of sensory, motor, and sensorimotor modules, exhibits "wall-following" behavior. From an external viewpoint, this behavior can appear deliberate and goal-directed, suggesting purpose, strategy, and perhaps even rudimentary intentions. Crucially, however, this robot lacks any internal system specifically designed for making decisions. "The robot does not have decisions built into it," Professor James explains. Its behavior is a direct consequence of its environmental sensing and its programmed movement responses. The wall-following emerges as an effective strategy based on its interaction with the environment, leading to an outward appearance of intentionality. The absence of a dedicated decision-making system in this machine prompts a provocative question: If a comparatively simple artificial system can generate behavior that mimics purposeful decision-making without an internal decision-making apparatus, could human behavior also appear to stem from centralized decisions even when no such singular process exists in the brain?
Professor James argues that this explanation, focusing on emergent behavior from interacting systems, is more parsimonious than postulating the existence of a "higher-level, central controller" within the brain that monitors and directs sensory and motor processes. The concept of such a central controller also introduces a long-standing philosophical quandary, dating back to Descartes. If a distinct entity within the brain is responsible for processing information and dictating actions, then the operation of this controller itself requires explanation. This leads to a potential infinite regress: to understand the controller, one might need to posit another, smaller controller within it, and so on. Professor James cites Daniel Dennett’s critique of this idea as the "Cartesian Theater," where positing an internal observer or decision-maker simply shifts the problem without solving it. Instead of invoking such an elusive internal arbiter, Professor James advocates for a direct examination of the interacting sensory and motor systems that collaboratively generate behavior.
This shift in perspective necessitates a corresponding evolution in experimental methodologies. If decision-making is understood as an emergent property of continuous, dynamic interactions among the brain, body, and environment, then research must move beyond strictly linear models. Investigators will need to design experiments capable of capturing the complexity of simultaneous processes, their mutual influences, and their continuous adaptation in response to environmental feedback. Professor James’s own laboratory is actively exploring this direction, integrating concepts from embodied cognition and ecological psychology. He believes this approach holds significant promise for unraveling the neural mechanisms that give rise to what we conventionally describe as decision-making. Furthermore, this integrated framework may offer novel avenues for investigating a wide range of other cognitive and mental phenomena that have traditionally been compartmentalized as distinct internal processes.
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