Neurosciences: your decisions, will you take them with or without emotions?

Too often, we still think that making a rational decision requires getting out of our emotions. To silence them. They would only be there to make us deviate from the path indicated by reason. This so-called Cartesian perspective - because it was inspired by the thought of the philosopher René Descartes - has nevertheless been called into question by three decades of research on the brain.

DIn an anti-Cartesian perspective, in fact, the best decision is one that correctly assesses what is beneficial to us by appealing to an emotional or affective feeling. Without this feeling, it is impossible to make a fair decision. This approach was popularized in the 1990s by neuroscientist Antonio Damasio through his book Descartes' mistake (Odile Jacob).

What if reality, in fact, was… in between? The sum of work carried out in cognitive science now shows that our emotions, if they can guide us towards the best decision taking into account our past experiences, can also deceive us. Limits that we can take into account when making important choices - provided we are warned.

The Phineas Gage case

In his book with the explicit subtitle, "the reason of the emotions", Antonio Damasio bases his argument on a historical case, that of an American who lived in the middle of the XIXe century. According to legend, Phineas Gage was a serious and uneventful foreman working on the construction of east-west railroad tracks. One day, a crowbar was propelled through his skull, a spectacular accident that would make him a medical "case".

To everyone's surprise, Phileas Gage was not dead. And besides, he was still talking. He did not seem to have lost either his intellectual capacities or his motor capacities. On the other hand, he had changed his personality! He had become rude, brawling, impulsive, and making a lot of bad decisions. "Phineas Gage is no longer Phineas Gage," said his doctor.

A century later, Antonio Damasio reconstructed the trajectory of the crowbar in Gage's brain. The researcher showed that the metal had passed through the mid-orbital regions of the prefrontal cortex. To explain the changes observed in Gage after his accident, he believes that this region is the seat of bodily sensations linked to emotional feelings. Thus, the memory of our past experiences would be supported by emotional cues called "somatic markers". These come into play when we consider different options before making a decision.

An unpleasant feeling, option rejected

When making a choice, we take into account several possible options, and each one will arouse particular sensations in our body - which we are not necessarily aware of. It is the “somatic marking”, product of our personal history. This phase directs us towards a privileged option, the one associated with the most positive feeling. An option associated with an unpleasant sensation in the body is interpreted as harmful by our brain, and automatically rejected.

From a Cartesian perspective coming from standard decision theory in economics, decision-making takes place differently. Faced with several options, the individual assigns a value to each, on the same scale. He can then compare the values ​​with each other. The option with the highest expected value then wins its decision.

It is likely, in light of the most recent work, that Cartesian and non-Cartesian modes of decision-making combine in our brain. The model drawn by the international community of researchers is becoming more refined and refined… it is becoming more complex. Also, thecontribution of perspective theory turns out to be important. Developed by two Israeli-American psychology professors, Daniel Kahneman and Amos Tversky, the former won the Nobel Prize in economics in 2002 - the latter having died.

See potential gains, or losses

This theory attempts to describe the behavior of individuals when faced with risky choices. If it has found its major application in finance, it describes springs that are not specific to the stock market and to traders. In fact, the experiments carried out by its two founders show that, for the same problem, the decision taken differs according to the way in which the problem is presented: in terms of its potential gains, or that of its losses, again potential. Depending on whether the individual adopts one or the other of these perspectives, however equivalent, he does not arrive at the same decision.

Behind this paradox, there is an explanation. When an individual calculates the value of each option before making a decision, those values ​​are not objective. There are a number of distortions that make them subjective. And in these distortions, emotions come into play, according to Daniel Kahneman and Amos Tversky.

A first experiment, seen from the point of view of gains, was carried out by the two researchers and published in the journal Science in 1981. The question is asked thus: you are a doctor and have the choice between two possibilities, either to save 200 people for sure, or to save 600 people but with only one chance in three to succeed.

Risk aversion

When the problem is presented in terms of gains - here the people saved - most subjects favor the rescue of 200 people without fail, rather than taking a risk. This highlights their aversion to risk.

The same principle applies for lotteries with monetary gains: between receiving 50 euros for sure, or one in two chance of winning 100 euros, the majority of subjects choose 50 euros for sure.

The third experiment of the two researchers leads the subjects to look at a choice from the point of view of losses. The question is asked this way: you have a choice between two possibilities, kill 400 people for sure, or kill 600 people but with only two in three chances of it really happening.

When the problem is presented from the point of view of losses, the subjects do not accept the certain loss. The majority choose the 2 in 3 chance of killing 600 people.

The explanation put forward by Daniel Kahneman and Amos Tversky is at the level of emotions. The idea of ​​killing is too emotionally off-putting, which explains the change in option of the majority of subjects. The fact of expressing sometimes one preference sometimes another, depending on how the problem is formulated, is a blatant case of irrationality, according to the two psychologists.

The amygdala activated during decision making

Neuroimaging experiments performed in MRI scans have shown that the amygdala, a region of the brain involved in emotional reactions, activates when the subject makes decisions. This latest discovery, reported in the review Science in 2006. , constitutes an argument in favor of an important role of emotions in decision-making.

There are undoubtedly variations among individuals. Thus, studies integrating the reaction to risk have been carried out by comparing traders and the general population. Traders have lower risk aversion - a characteristic which would be linked to lower emotional reactions. Thus, it seems that the more intense the emotional reactions, the more people have a marked aversion to risk.

Ongoing work at the Brain and Spinal Cord Institute (ICM) is testing the hypothesis that our mood influences how we weight gains and losses. A bit like in the parable of the half empty and half full glass… A person in a good mood would put more emphasis on the gains while a person in a bad mood would tend to stress on the losses.

While waiting for further advances in knowledge, how can we make decisions taking our emotions into account, but without letting them “fool” us? It's up to us to play finely on emotional regulation. One technique consists in convincing oneself, when making the decision, that it is only one among many others, so as not to be overwhelmed by emotion. This is undoubtedly what René Descartes would have advised ...

Be careful, however, not to switch to the opposite excess. Too much coldness, too much indifference is not the solution either, as Antonio Damasio reminded us. Let's find a middle way by becoming aware of our emotional feelings in order to be able to make decisions accordingly, without falling into automatic reactions which very often prove to be inappropriate.

Mathias Pessiglione, Researcher in cognitive sciences, clinical psychologist, Brain and Spine Institute (ICM)

La original version of this article was posted on The Conversation.

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