how do we make decisions?

To make decisions, new research has found that our brains are constantly doing calculations that enable us to keep track of relationships between changing factors. For complex decisions based on many independent factors, like whether we buy a car now or save the money for a trip, our brains look at how the factors correlate with each other, according to work @ California Institute of Technology (Caltech) and University College London.

These relationships/correlations allow observing the outcome of one action and then guessing the outcomes of other related actions or events without having to, or being able to, experience each of them individually. This leads to quicker responses than if we made all choices based on trial and error or mental historical “rules of thumb”, as scientists used to believe.

This study, published this month in Neuron, also identifies the regions of the brain involved in tracking these correlations/relationships.

The researchers scanned the brains of 16 subjects using functional magnetic resonance imaging (fMRI), which measures activity in the brain from the effects of consumption of glucose and oxygen in the blood (BOLD), while the subjects played a game of resource management. The subjects were to adjust the proportion of energy coming from two renewable energy sources — a solar plant and a wind farm—in an effort to create the most stable energy output possible.

The outcomes of the two energy sources varied with each other. So, for example, when they were strongly correlated, the wind blew while the sun was shining, so each source generated power. The researchers changed the correlation between the two sources throughout the experiment, requiring the subjects to continuously revise their predictions of the outcomes of those correlations.

The team found that the subjects changed their behaviors to reflect new correlations far faster than they could have had they been relying on a simple trial and error approach. They were estimating the correlation between the sources, tracking mistakes in their estimations, and adjusting estimates of the correlation in real time.

Klaus Wunderlich, lead author of the Neuron paper, began designing the study while a graduate student at Caltech. Now at University College London, Wunderlich says there is an evolutionary importance to such correlations. “Evolutionary importance” means that folk who were better at developing these correlations were more likely to survive and pass their genes on for future generations. “Imagine our ancestors foraging for food in the woods. They could spend their time either collecting berries or hunting deer,” he says. “Now imagine they have previously observed that deer eat berries. So, as they are foraging, if they notice a lack of fresh berries, they can infer that there are lots of deer around and instead focus on hunting.”


When the researchers looked at the fMRI scans of the subjects during the game, they saw increased activity in two regions of the brain commonly associated with emotion — the insula and the anterior cingulate cortex (ACC). They believe that the brain makes predictions about correlation strengths in the insula and then tracks the accuracy of its predictions in the ACC.

Functional magnetic resonance imaging (fMRI) measurements show the neural activity in two parts of the brain when a subject plays a resource management game. The activity in the insula (left) is related to making predictions about correlation strengths, while activity in the ACC (right) is related to tracking the accuracy of such predictions. (Credit: K. Wunderlich, M. Symmonds, P. Bossaerts, and R. Dolan / Neuron)

Bossaerts says that the location of these correlation-forming and outcome-tracking functions in regions of the brain often thought of as “emotional” provides additional evidence that rational mathematical thinking and emotions are not at odds.
“It is integral to good decision-making to be emotional,” he says. “Being completely emotion-free can be detrimental, especially when making decisions under uncertainty.”

Of course, as all readers of this blog know, "we" only apparently make decisions. As this article clearly attests, the brain is rapidly doing the correlations, estimations and comparisons through these centers of which we have no understanding or control - most folk have no idea that they even exist. The quote that "They (the subjects) were estimating the correlation between the sources, tracking mistakes in their estimations, and adjusting estimates of the correlation in real time." shows how incorrect, but ingrained, the perception is that WE make decisions.