We, generally, tend to make judgements based either on reason or on a ‘gut feeling’. Our judgements are based not only on experience and relevant information but also on our preferences. The question of whether human reasoning is biased by desires and goals is crucial for everyday social, professional and economic decisions. Although how much of our belief formation is influenced by what we want to believe is still debated, a new study confirms that belief updates are, indeed, optimistically biased. The study, conducted by the Max Planck Institute for Metabolism Research (Cologne) successfully shows that a reward system in our brain conveys judgements affected by one’s own desires.
Published in The Journal of Neuroscience, the study asked volunteers to estimate the average and personal risk of various negative events. During the survey, the scientists recorded brain activity of volunteers using magnetic resonance tomography (MRT), an imaging technique that is able to show the alteration of tissue structure and function with very low risk for the patient. This was followed by informing the participants of the actual average risk associated with a particular event, at which point, they were asked to adjust their own risk estimates accordingly.
“In complex, confusing situations, we run the risk of making a biased judgement as soon as we prefer one conclusion over another,” explains Dr Bojana Kuzmanovic, a scientist at the Max Planck Institute for Metabolism Research. She has investigated the process by which people’s judgement is influenced by their wishful thinking. Dr Kuzmanovic explains the occurrence using an example: “By ignoring unpleasant information, we avoid drawing threatening conclusions. For example, we could neglect federal statistics, which indicate a higher risk of heart attack, because we think we have a particularly healthy lifestyle.”
The MRT imaging scans showed that preferred judgements activate brain regions that otherwise react particularly strongly to rewards such as food or money. Additionally, for the first time, scientists were able to show that the reward system, in turn, influenced other brain regions involved in conclusion processes. The stronger this neuronal influence, the more strongly judgements were determined by volunteers’ wishes.
The research indicates that our desires and preferences influence our judgement without any conscious realisation on our part. It seems that the same brain systems that reinforce our efforts to maximise rewards, such as food and money, would also reinforce specific strategies for constructing judgements. Dr Marc Tittgemeyer, the lead scientist on the study, says, “The influence of preferences is independent of expertise. We can benefit from this pleasant self-strengthening effect as long as our judgements do not have serious consequences. However, when making important decisions, we should be aware of our tendency to distort judgement and apply strategies to increase objectivity.”
In future, the research team plans to investigate whether these and other reward-dependent behaviours are different in patients with metabolic diseases than in healthy individuals. It is believed that reward-dependent brain circuits are closely linked to homeostatic circuits that regulate energy demand and metabolism, based on saturation and hunger signals. Hence, if homeostatic networks are altered by disease, it could affect reward-dependent brain areas and, possibly, lead to more impulsive behaviour.