RESEARCH ARTICLE Pupil dilation prediction of random events [version 2; referees: 2 approved with reservations]

We report the results of a conceptual replication of a study that reported that pupil dilation can predict potentially threatening random events above chance level. In this study, participants ’ pupil dilation was used to predict the appearance of a threatening or a neutral stimulus, presented randomly in a double sequence of ten trials with replacement, i.e. replacing the chosen trial for the future extractions. In the first experiment, with a sample of 100 participants, the average correct prediction was 55.9%, with a small difference between the two stimuli. This effect was further tested in an exact pre-registered study where the average correct prediction was 58.7%. The reliability of these findings was checked utilizing both a frequentist and a Bayesian statistical parameters estimate approach. These findings collectively support the hypothesis that pupil dilation can be used to anticipate random and therefore theoretically “unpredictable ” events in an implicit unconscious way that is without a conscious awareness, and that this ability is another characteristic of the powerful anticipatory adaptive systems of our psychophysiological system