Brain’s Decision Making Algorithms Decoded


“Truly successful decision-making relies on a balance between deliberate and instinctive thinking.”
― Malcolm Gladwell

It is still a young field, but research in decision neuroscience has skyrocketed in the last decade.

Scientists are beginning to decipher precisely what is happening in our brains when we are making choices, whether they be big or small.

And now, a new brain-imaging study from The University of Texas at Austin is the first to combine computer simulations with brain-imaging data to contrast two different types of decision-making models.

When making a choice, the brain retrieves specific traces of memories, instead of a generalized overview of past experiences, from its mental files, the study found.

In one decision making model, called the exemplar model, a decision is framed around concrete traces of memories.

In the other model, the prototype model, decisions are based on a generalized overview of all memories lumped into a specific category.

Exemplar Decision Making Model

Whether one model creates decisions more than the other has been in dispute among scientists for more than three decades.

Now, according to the findings, the exemplar model is more consistent with decision-making behavior.

In the study, 20 respondents were asked to sort a variety of shapes into two categories.

During this task, their brain activity was watched using functional magnetic resonance imaging (fMRI). This allowed researchers to observe how the respondents connect shapes with past memories.

Visual, Sensory and Attention Tasks

According to the findings, behavioral research alone cannot determine if a subject uses the exemplar or prototype model to make decisions.

With brain-imaging analysis, researchers found that the exemplar model is responsible for the majority of participants’ decisions.

Their results show three different regions associated with the exemplar model were activated during the learning task: occipital (visual perception), parietal (sensory) and frontal cortex (attention).

In processing new information, the brain stores actual traces of experiences, allowing it to make different kinds of decisions, such as categorization information (is that a plant?), identification (is that Jane’s plant?) and recall (when did I last see this plant?).

Model-based Cognitive Neuroscience

“For example”, study lead Michael Mack says, “imagine having a conversation with a friend about buying a new car. When you think of the category “car,” you’re likely to think of an abstract concept of a car, but not specific details. However, abstract categories are composed of memories from individual experiences. So when you imagine “car,” the abstract mental picture is actually derived from experiences, such as your friend’s white sedan or the red sports car you saw on the morning commute.”

We flexibly memorize our experiences, and this allows us to use these memories for different kinds of decisions,” Mack says. “By storing concrete traces of our experiences, we can make decisions about different types of cars and even specific past experiences in our life with the same memories.”

According to the psychology and neuroscience researcher, this new approach to model-based cognitive neuroscience could lead to discoveries in cognitive research.

“The field has struggled with linking theories of how we behave and act to the activation measures we see in the brain,” Mack says. “Our work offers a method to move beyond simply looking at blobs of brain activation. Instead, we use patterns of brain activation to decode the algorithms underlying cognitive behaviors like decision making.”

Impacts and Theories

“Our new knowledge about the cellular and circuit mechanisms of working memory and decision processes in the brain has already had a significant impact on clinical studies of mental illness,” said Xiao-Jing Wang, PhD., Yale University School of Medicine. “For instance, addiction is fundamentally a problem of making bad choices, resulting from impaired reward signaling and decision-making circuits in the brain. Understanding these circuits has become key to linking genes and molecules with behavior in clinical studies."

“For many psychiatric disorders, patients that are symptomatic are frequently making poor decisions about numerous things throughout the day, such as how they handle their anxiety and other emotional states,” adds C. Daniel Salzman, MD, PhD., Columbia University School of Medicine. “If you’ve ever had a friend or family member with depression, you can see they are not making decisions the way they normally do. So there clearly has to be dysfunction in the neurocircuits of psychiatric patients affecting their decisions, and we need to understand this better in order to come up with better treatments for mental disorders.”

It seems that emotion aids in the decision making process. Decision making often happens in the face of uncertainty about whether one’s choices will lead to benefit or harm.

The somatic-marker hypothesis is a neurobiological theory of how decisions are made in the face of uncertain outcome.

This theory holds that such decisions are aided by emotions, in the form of bodily states, that are elicited during the deliberation of future consequences and that mark different options for behavior as being advantageous or disadvantageous.

This process involves an interplay between neural systems that elicit emotional/bodily states and neural systems that map these emotional/bodily states.

Although it is unclear whether the studies generalize to all processing, subconscious processes have also been implicated in the initiation of conscious volitional movements.

Michael L. Mack, Alison R. Preston, Bradley C. Love
Decoding the Brain’s Algorithm for Categorization from Its Neural Implementation
Current Biology, Volume 23, Issue 20, 2023-2027, 03 October 2013 10.1016/j.cub.2013.08.035