Summary: A theoretical neuro-philosophy and cognitive neuroscience framework challenged the foundational scientific consensus regarding how the brain processes decisions. The research dismantles the long-standing linear “sandwich model”, which defines decision-making as a discrete, high-level cognitive engine wedged cleanly between sensory perception and motor action.
Instead, the framework demonstrates that the brain lacks any localized neural process for decision-making, revealing that what we perceive as a conscious choice is actually an emergent property of simultaneous, circular interactions between sensory, sensorimotor, and motor mechanics.
Key Facts
- The Sandwich Model Fallacy: Traditional scientific theories and everyday intuitions assume a linear causal sequence where the brain acts as a three-stage processor, moving from sensory perception, to a cognitive decision, to a motor action.
- The Missing Cognitive Link: While the brain possesses clear, specialized neural networks dedicated to sensing the environment and executing physical movements, it features no corresponding, discrete neural processes specifically for making decisions.
- The Action Selection Shift: In place of a localized, top-down decision control system, the framework argues that a dynamic mixture of sensory, sensorimotor, and motor processes drives what is more accurately termed “action selection”.
- The Nonphysical Abstract Entity: Utilizing a physicalist framework, the research argues that decisions are abstract, nonphysical entities that cannot physically cause actions. Like an object’s center of mass, a decision is a useful conceptual description of behavior, but it cannot exert independent physical force.
- The Cartesian Theater Paradox: Postulating a high-level central controller inside the mind creates a logical fallacy known as the Cartesian Theater. This model implies a miniature person sits inside the brain to make choices, requiring an infinite regress of smaller controllers inside controllers without ever explaining how the brain actually functions.
- The Emergent Robot Proof: The paper highlights a simple robot built with only basic sensory and motor modules that exhibits complex, intentional-looking wall-following behavior. Despite having no internal decision-making systems or strategic controllers, the machine’s interaction with its environment gives the illusion of choice.
- The Embodied Path Forward: Author Tom James, a professor in the Department of Psychological and Brain Sciences, asserts that cognitive neuroscience must abandon linear models and develop new experimental methods rooted in embodied cognition and ecological psychology to map the simultaneous, circular loops binding the brain, body, and environment.
Source: Indiana University
There is a disconnect, suggests Indiana University Professor Tom James, between what we think happens when we make a decision and what happens in the brain during that process.
In both prevailing scientific theories and common-sense views, decisions have long been defined as an intermediate stage between perceptions and actions with each stage of this linear causal sequence corresponding to a discrete brain function, from sensory to cognitive to motor.
Scientific methodologies that study this process, particularly model-based cognitive neuroscience, tend to both reflect and reaffirm the assumption of a linear causal sequence. Our intuition confirms it as well. As James notes, “Our actions feel like they are caused by decisions based on desires, beliefs, and intentions.”
And yet, says James, this linear explanation, often referred to as the “sandwich model,” does not add up when we consider how the brain works. For one, while both sensing and acting have corresponding sensory and motor mechanisms in the brain, the cognitive, decision-making stage between them does not appear to have any corresponding neural processes.
In place of a discrete decision-making function in the brain that causes actions, James argues that a combination of sensory, sensorimotor, and motor processes leads to what he prefers to call ‘action selection.’ And it is based on a less linear, more simultaneous and circular interaction between body, brain, and environment – a feature which calls for a shift in scientific methods that can capture this dynamic.
This is not to suggest that decisions don’t exist.
As James says, “Of course they do. We use this language all the time and it’s very helpful in terms of describing behavior. 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.”
James, a professor in the Department of Psychological and Brain Sciences in the College of Arts and Sciences, lays out his argument in “Sensorimotor Mechanisms of Decisions and Actions,” an article just published in the Journal of Cognitive Neuroscience.
What happens in the brain when we make a decision?
To develop his argument, James makes use of a “physicalist” framework outlined by philosophers like Daniel Dennett, making explicit the principles on which he believes science depends.
According to this view, only physical phenomena, which include sensory and motor processes, can cause physical and nonphysical phenomena. Nonphysical phenomena, such as decisions, cannot cause actions or other physical phenomena.
James introduces a series of analogies to further explain.
Borrowing Daniel Dennett’s idea of the self as analogous to a center of mass (CoM) or center of gravity, James proposes that like the CoM, a mathematical concept that by itself cannot exert a physical influence – i.e., you cannot move an object’s center of mass without moving the object – decisions are a similarly abstract, nonphysical entity.
A second analogy highlights the gap between the concepts we use to communicate and what we might observe at a finer level of analysis. For example, we routinely refer to “the university” to explain in a general way what is happening within it.
The word is an abstract entity, which conveniently stands in for the collection of people and buildings of which the university is comprised. And yet, if we say that “the university took certain actions during a campus protest,” for example, to describe an event that took place, it does not give us a precise picture of what transpired, the meetings between administrative officials, the phone call to state police, etc. that would give us the level of detail we might want to understand what took place on that day.
Likewise with decisions, James maintains: “As mental phenomena, they are defined on too abstract a level for the goals of cognitive neuroscience.” They do not enable us to understand what is happening in the brain.
A third example pushes the argument to its logical conclusion:
James finds a compelling model for human decision-making in a robot built with a few simple, sensory, motor, and sensorimotor modules. The robot exhibits a “wall-following” behavior that appears intentional, appears to reflect goals and strategies, despite the lack of such abilities.
“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.”
If the robot, which has no capacity to make decisions or develop strategies, nonetheless gives the appearance of decision-making behavior, isn’t it possible that we might do the same? It’s a more parsimonious explanation, James argues, than that which relies on what he calls “a higher-level, central controller that monitors and regulates sensory and motor processes.”
That notion of a “higher-level, central controller,” moreover, can lead to some paradoxical reasoning, which philosophers have observed since the time of Descartes. “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,” says James.
“Dennett called this idea the Cartesian Theatre. That person inside your brain would need another person inside its brain, which would need a person inside its brain and so on, in an infinite regress. So the problem is never solved. It’s just passed on.”
An experimental path forward
James’s argument leaves off with some exhilarating, yet daunting challenges with respect to the experimental methods needed to disentangle a less linear, more simultaneous or circular interaction between the brain, body, and environment that make up what we call decision-making.
He has begun to take up the challenges in his own lab by drawing on theories of embodied cognition and ecological psychology. He sees this as the path forward if cognitive neuroscience is to gain a better grasp of the mechanisms behind decision-making and, perhaps, a host of other cognitive and mental phenomena.
Key Questions Answered:
A: Because human language is highly optimized to describe behavior on an abstract level. While choices absolutely exist as a helpful way to communicate our actions, the physical brain does not actually require a localized control process to generate that behavior; it produces intentional-looking results purely through the simultaneous interaction of our senses and muscles.
A: It is a logical trap where you try to explain the brain by putting a tiny captain inside it. If you claim a central controller monitors your thoughts and makes choices, you haven’t solved the mystery of the mind; you have just introduced a miniature person who would then need an even smaller person inside their own head, passing the problem down an endless loop.
A: It proves that complex, strategic behavior can emerge without any internal blueprint for strategy. The robot contains nothing but basic sensory and motor modules; it simply reads its environment and moves, yet its actions look completely intentional and goal-driven, proving that human decision-making might just be an illusion born from simple physical loops.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this neuroscience research news
Author: Elizabeth Rosdeitcher
Source: Indiana University
Contact: Elizabeth Rosdeitcher – Indiana University
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Sensorimotor Mechanisms of Decisions and Actions” by Thomas W. James. Journal of Cognitive Neuroscience
DOI:10.1162/JOCN.a.2484
Abstract
Sensorimotor Mechanisms of Decisions and Actions
Decisions are often thought of as an intermediary between perception and action, but the degree to which this assumption is integrated into different parts of cognitive neuroscience theory and practice varies.
After examining these variations on the causal relationship between decisions and actions, this perspective will argue for the claim that decisions and decision processes do not cause actions. An argument will be made that, in place of decision processes, actions are caused by sensorimotor processes.
Lastly, ideas are given for studying the sensorimotor processes involved in decisions and actions.
The main recommendation is a move to more ecological testing environments that give participants agency over their actions and allow them to learn by continuously updating sensorimotor processes through active sensing.
