Pupil dilation prediction of random events

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.