Without you even noticing it, your brain – just like the RIVM – is busy all day calculating scenarios.

Throughout the day, people have to make all kinds of decisions. Will you cross the street soon? Or are you waiting? Do you take the elevator or the stairs? Is now the time to start investing or not? And every time you make a decision, you do it with a certain amount of confidence. But what is that trust based on? Dutch brain researchers have looked it up and discovered that we base the degree of certainty with which we make a decision on the number of possible scenarios that our brain calculated shortly before – without our being aware of it. And with that you can actually compare our brain a bit with the RIVM, which is also constantly working on different scenarios during this pandemic in order to make decisions or issue advice based on them.

Method

The brain researchers base their conclusions on experiments. They gathered a number of test subjects, who then sat down in an MRI scanner that measured their brain activity. “Once in the MRI scanner, the subjects were asked simple questions based on visual observations,” explains first author Laura Geurts. “They were shown images with black and white lines in different orientations: in one image they were horizontal, in the other vertical or something in between.” After the subjects had seen such a picture, they were asked about the orientation of the stripes.

“Because we know quite well how what the subjects saw is translated into brain activity, we were also able to measure which interpretations of the picture (ie: scenarios) the subjects considered,” says Geurts. “And based on the brain activity, we were also able to calculate the probability of the different scenarios.” The research reveals that the brain calculates several scenarios before making a decision and then chooses the best one. “We then asked the subjects how confident they were in their decision. And this shows that the feeling of certainty is based on the number of possible scenarios that the brain has calculated.” The less likely the alternative scenarios the subjects’ brains had calculated, the more certain the subjects were about their decision.

Subjective

It is an interesting finding. “The feeling of certainty about a decision is very subjective,” says researcher Janneke Jehee. “And until recently, we didn’t know exactly what that feeling was based on.” Researchers did have ideas about this. “Some scientists suspect that the feeling of security is based on a kind of rules of thumb,” explains Geurts. She illustrates this hypothesis with an example. “Suppose you want to cross a street, then you have to decide whether it is safe to do so. This can depend on various factors: for example, the degree of crowds and whether you have good visibility. Some researchers think that the degree to which we have confidence in our ultimate decision to cross the road – or not – is based on rules of thumb that relate, for example, to how busy it is on the street.” In that case, the brain would get rid of it quite easily. “It’s a kind of shortcut, a trick.” However, based on the research by Geurts and colleagues, the reality turns out to be more complex: the brain calculates various scenarios prior to a decision, like a real supercomputer, and the degree to which we have confidence in the decision depends on the number of possible alternative scenarios.

Applications

“It’s important to know exactly how that confidence in our own decisions comes about,” says Jehee. “Because we can ultimately apply that knowledge in various, very concrete ways. For example, we know that people with a psychiatric disorder are less able to estimate their certainty about decisions. And children and adults who are well able to estimate their security are known to usually learn better. More insight into the processes underlying that certainty can ultimately lead to therapies and teaching methods that are specifically developed to increase the proper assessment of confidence in one’s own decisions.”

However, more research is needed before scientists can explore such applications further. One of the most important follow-up questions is whether our confidence in complex decisions is established in the same way. This is in line with expectations, but has certainly not yet been proven on the basis of the experiments – in which test subjects had to make a fairly simple decision. “Especially with complex decisions, the brain has to calculate many different scenarios,” says Jehee. “That means that the brain must first determine which scenarios are conceivable and then weigh them all up against each other. Certainly in the case of complex decisions, it may just be that there are also scenarios in which the parameters cannot be accurately predicted – something that, for example, the RIVM also regularly struggled with during the pandemic.” And then it is very interesting what will happen. “Because then you may be quite sure of your decision purely on the basis of the number of alternative scenarios calculated, while in reality it is very uncertain.”