“Strength of conviction won’t help to persuade when people disagree” [Medical Xpress/University College London]

“Strength of conviction won’t help to persuade when people disagree

by University College London


If you disagree with someone, it might not make any difference how certain they say they are, as during disagreement your brain’s sensitivity to the strength of people’s beliefs is reduced, finds a study led by UCL and City, University of London.

The brain scanning study, published in Nature Neuroscience, reveals a new type of confirmation bias that can make it very difficult to alter people’s opinions.

“We found that when people disagree, their brains fail to encode the quality of the other person’s opinion, giving them less reason to change their mind,” said the study’s senior author, Professor Tali Sharot (UCL Psychology & Language Sciences).


Professor Sharot added: “Opinions of others are especially susceptible to the confirmation bias, perhaps because they are relatively easy to dismiss as subjective. Because humans make the vast majority of decisions—including professional, personal, political and purchase decisions—based on information received from others, the identified bias in using the strength of others’ opinions is likely to have a profound effect on human behaviour.”


Confirmation bias in the utilization of others’ opinion strength

Andreas Kappes, Ann H. Harvey, Terry Lohrenz, P. Read Montague & Tali Sharot

Nature Neuroscience (2019)


Humans tend to discount information that undermines past choices and judgments. This confirmation bias has significant impact on domains ranging from politics to science and education. Little is known about the mechanisms underlying this fundamental characteristic of belief formation. Here we report a mechanism underlying the confirmation bias. Specifically, we provide evidence for a failure to use the strength of others’ disconfirming opinions to alter confidence in judgments, but adequate use when opinions are confirmatory. This bias is related to reduced neural sensitivity to the strength of others’ opinions in the posterior medial prefrontal cortex when opinions are disconfirming. Our results demonstrate that existing judgments alter the neural representation of information strength, leaving the individual less likely to alter opinions in the face of disagreement.”

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