Department of
Psychological and Brain Sciences

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.