We humans prefer happy ending – experiences that end well. We draw conclusions for future situations and decisions from such experiences. But this is precisely what sometimes goes wrong and leads to wrong decisions, because we tend to overestimate the good end. Researchers have now found out what mechanisms are behind this in the brain.
People make their decisions based on experience. They evaluate past experiences and can deduce from them, for example, whether they would like to experience something similar again or would rather avoid it. However, some of these classifications happen unconsciously and observations suggest that the end of an experience is weighted disproportionately. The lessons that we draw from an experience may not necessarily be the right subjectively. Such cognitive distortions often lead to wrong conclusions and irrational decisions. A classic example is the so-called “banker’s fallacy”, which leads to people overestimating short-term upward trends and taking long-term developments too little into account.
The last moments count most
Researchers led by Martin Vestergaard from the University of Cambridge have now conducted a study using functional magnetic resonance imaging (fMRI) to investigate how people make decisions and which cognitive mechanisms play a role in this. “When deciding which restaurant to dine in, think about where you’ve had a good meal in the past. But your memory of whether that meal was a good one isn’t always reliable – our brain weighs the last moments of the experience more heavily than the rest of the experience, ”explains Vestergaard. “If we can’t control our built-in attraction to happy endings, then we can’t trust that our decisions are really good for us.”
Using a game experiment, the researchers succeeded in reproducing this effect precisely. 27 test persons were asked to decide which of two coin pots had the higher total value. To do this, they saw a row of coins from each of the two pots in quick succession, larger coins being more valuable than small ones. The brain scanner recorded what was going on in the subjects’ brains. The task was repeated several times, with both the number of coins shown and their sequence varying: sometimes the large – i.e. valuable – coins appeared at the beginning of the sequence, sometimes towards the end.
Cognitive biases lead to irrational decisions
Almost all test persons decided against a pot if the size of the coins decreased towards the end of the sequence – even if the total value of the coins shown was actually higher than in the other pot. A bad ending overshadowed the positive overall course in their decision-making. How strong this effect was varied from person to person. Few, however, were able to ignore him entirely.
The results thus confirm theoretical models and replicate previous research. For the first time, however, the researchers were able to understand which cognitive mechanisms the decision is based on. As they found out, the overall course of an event is coded in the amygdala, a region of the brain that is responsible, among other things, for the emotional evaluation of situations. In contrast, whether the sequence develops positively or negatively towards the end is processed in the anterior insula, a part of the cerebral cortex that is involved in sensory perception, among other things.
Separate brain regions for end and course
The more active the anterior insula was in the subjects, the more likely they were to neglect the overall course and to be deceived by the tendency at the end of the coin sequence. In contrast, high amygdala activity was more often associated with correct decisions. The current study thus contradicts previous assumptions, according to which the amygdala is a primitive part of our brain that tends to conflict with rational decisions.
According to the researchers, focusing on the last moments of an experience is a fundamental mechanism in the human brain. In many life situations it can be important to pay attention to whether things are in an upward or downward trend. However, if this information is used to evaluate an overall experience, this leads to a distorted judgment. When it comes to deciding on a good restaurant, a fallacy has hardly any serious consequences. In other contexts, however, it can be very relevant to become aware of possible cognitive biases.
“Many politicians who are seeking re-election take advantage of the fact that we are increasingly remembering the last moments of an episode and include them in our decisions; they will always try to appear strong and successful towards the end of their term, ”says Vestergaard. “If you fall for this trick and ignore previous incompetence and failures, you could end up re-electing an unsuitable politician.” According to the researcher, it is therefore worth taking time to pause and reflect. “A more analytical approach to complementing your intuitive judgment can help you make a rational decision.”
Source: Martin Vestergaard (University of Chicago) et al., Journal of Neuroscience, doi: 10.1523 / JNEUROSCI.2130-19.2020