People are motivated to adopt the most favorable beliefs about their future because positive beliefs are experienced as rewarding. However, it is so far inconclusive whether brain regions known to represent reward values are involved in the generation of optimistically biased belief updates. To address this question, we investigated neural correlates of belief updates that result in relatively better future outlooks, and therefore imply a positive subjective value of the judgment outcome. Participants estimated the probability of experiencing different adverse future events. After being provided with population base rates of these events, they had the opportunity to update their initial estimates. Participants made judgments concerning themselves or a similar other, and were confronted with desirable or undesirable base rates (i.e., lower or higher than their initial estimates). Belief updates were smaller following undesirable than desirable information, and this optimism bias was stronger for judgments regarding oneself than others. During updating, the positive value of self-related updates was reflected by neural activity in the subgenual ventromedial prefrontal cortex (vmPFC) that increased both with increasing sizes of favorable updates, and with decreasing sizes of unfavorable updates. During the processing of self-related undesirable base rates, increasing activity in a network including the dorsomedial PFC, hippocampus, thalamus and ventral striatum predicted decreasing update sizes. Thus, key regions of the neural reward circuitry contributed to the generation of optimistically biased self-referential belief updates. While the vmPFC tracked subjective values of belief updates, a network including the ventral striatum was involved in neglecting information calling for unfavorable updates.

HighlightsThere are a number of controversial questions regarding the nature and causes of unrealistic optimism.We argue that unrealistically optimistic cognitions should be considered beliefs rather than desires or hopes.Optimistically biased beliefs are frequently false but establishing falsity in individual cases is difficult and sometimes impossible.Optimistically biased beliefs are epistemically irrational because they are unwarranted and their responsiveness to counter-evidence is limited.

People learn more from new information when it leads to favorable future outlooks and thus can maintain optimism despite conflicting evidence. In two studies (N = 20 and 26), we investigated whether this optimism bias in belief updating is self‐specific by modifying a recently introduced learning paradigm. In each trial, participants had to estimate the probability of experiencing a negative future event, were then presented with the population base rate of that event, and were subsequently asked for a second, updated estimation. In half of the 88 trials with varying events, estimations were made for oneself, in the other half for a similar other. We tested whether the updates (differences between the first and second estimates) following undesirable base rate were lower than those following desirable base rates, and whether this difference was greater for self relative to other. In both studies, the overall results support the presence of a self‐specific optimism bias in belief updating. However, taking into account trait optimism (TO) as a moderator variable revealed that this was the case only in participants with high TO, whereas those with low TO showed optimistic belief updating for both self and other. In Study 2, we additionally controlled for possible misclassifications of base rate desirability. Taken together, the optimism bias in belief updating was demonstrated by a selective neglect of unfavorable information. A self‐specific influence of this bias in individuals with high TO may ultimately cause the impression of a more positive future outlook relative to others. Copyright © 2014 John Wiley & Sons, Ltd.

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