Аннотация:Human behavior in probabilistic environment is characterized by a preference for a more frequently reinforced option, yet people tend to make a few number of disadvantageous choices as well. We test the hypothesis that risky choices may reflect a bias to search for regularities in a random sequence of events. We meas-ured pupil dilations as a marker of norepinephrine release in locus coeruleus, which may index subjects’ engagement in the exploratory behavior. Fifty-two healthy participants performed two-alternative serial choice task with the reward probability of 0.7 for one stimulus and 0.3 for the other. Feedback was presented with a delay of 1 sec after the response. We performed ANOVA analysis of mean pupil area in a 1400-ms time window following feedback onset. We con-sidered three factors that could trigger pupil dilations: riskiness of the current choice, its positive or negative outcome, and the riskiness of the following choice. We found that pupil dilation predicted the future risky choice, while it did not de-pend on the other two factors. The amplitude of pupil dilation before a persistent risky decision negatively correlated with the total number of risky choices. Taken together, these findings indicate that the latent process of preparation for risky de-cisions is associated with increased norepinephrine release. We suppose that the transitory increment of norepinephrine release may result from detection of a con-flict between the pragmatic model of the advantageous strategy and the planned risky action by the cingulate cortex, which sends excitatory projections to the lo-cus coeruleus.