Prejudice confirmation found in prefrontal cortex

Prejudice confirmation found in prefrontal cortex
Schematic representation of the first and second part of the experiment Andreas Kappes et al. / Nature Neroscience, 2019

Conviction of one’s own rightness prevents one from objectively assessing the strength of another’s argumentation, if opinions differ, but allows accepting it if they coincide. This was found out by British scientists who conducted an experiment using fMRI. It turned out that the assessment of the posterior part of the medial prefrontal cortex, which activity does not change if opinions do not coincide, limits the assessment. The discovered mechanism explains the work of confirmation bias – cognitive distortion, in which a person is inclined to choose from all information only that which confirms his opinion, scientists write in Nature Neuroscience.

The information that a person receives daily can confirm his already existing opinion on any issue, or refute it. In any case, an established opinion must be somehow updated, which requires some flexibility in front of new information. In fact, everything is not so simple, a person is sufficiently biased in the matter of confirming (or refuting) his opinion: often in such situations, he is subject to one of the cognitive distortions – confirmation bias. 

The psychological basis of confirmation bias has been studied quite well, and little is known about the neural mechanisms that underlie it. To fix this, scientists decided under the leadership of Andreas Kappes from the University of London. In their experiment, 42 people took part, who were divided into pairs. Each of them passed a small survey to assess the value of real estate: for example, whether the house shown to them is worthless or more than a million dollars. 

After that, the participants were placed in pairs in two tomographs, located opposite each other and separated by a transparent wall. Each of the two participants was shown at first a certain house with a specific rate, then an opinion about the cost of the other participant (lower or higher), and then how much he put money on it. The money was real (from 1 to 60 cents) – their participants could take it after the experiment, and receive it if their judgment turned out to be correct, that is, the house actually cost either less or more than the specified amount. Otherwise, the indicated amount was subtracted from the final.

Thus, each participant could either pay attention to the opinion of the other or not, and update the indicated rate in order to gain more or lose less money. It turned out that if one participant saw that the second rated the house the same way, then he was more willing (p <0.001) to change his bid than if their opinions differed or there was no information about the rate of the other at all. In other words, the participants were more supportive of the opinion of another, if it confirmed the opinion of themselves, and ignored if it was different.

The fMRI data showed that if the opinions of the two participants were the same, the bidder had a statistically significant (p <0.001) inverse correlation between the activity of the posterior part of the medial prefrontal cortex and how high the rate of the second participant was. In other words, the lower the partner’s bid in the event that he evaluated the lot in the same way, the more the considered area is activated. If opinions differed, there were no changes in the activity of the site. 

The prefrontal cortex is known to play an important role in decision-making, and the specific area – the back of the medial prefrontal cortex – is activated when receiving information that may affect the decision after it has already been made. The authors of the work showed that the activity of this site reflects the whole essence of the bias of confirmation: to the information that confirms the established opinion, man listens more than to the one that contradicts it.