F1000Research Open Peer Review , National Institute of Mental Chris Baker Health USA , Immunexpress Inc. USA Leo McHugh Discuss this article (0) Comments 2 1 RESEARCH ARTICLE Pupil dilation prediction of random events [version 2; referees: 2 approved with reservations] Patrizio E Tressoldi, Massimiliano Martinelli, Luca Semenzato Dipartimento di Psicologia Generale, Università di Padova, Padova, 35131, Italy Abstract 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. Patrizio E Tressoldi ( ) Corresponding author: Patrizio.tressoldi@unipd.it Tressoldi PE, Martinelli M and Semenzato L. How to cite this article: Pupil dilation prediction of random events [version 2; referees: 2 2014, :262 (doi: ) approved with reservations] F1000Research 2 10.12688/f1000research.2-262.v2 © 2014 Tressoldi PE . This is an open access article distributed under the terms of the , Copyright: et al Creative Commons Attribution Licence which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Data associated with the article are available under the terms of the (CC0 1.0 Public domain dedication). Creative Commons Zero "No rights reserved" data waiver The author(s) declared that no grants were involved in supporting this work. Grant information: Competing interests: No competing interests were disclosed. 02 Dec 2013, :262 (doi: ) First published: 2 10.12688/f1000research.2-262.v1 Referee Status: Invited Referees version 2 published 09 May 2014 version 1 published 02 Dec 2013 1 2 report report report report 02 Dec 2013, :262 (doi: ) First published: 2 10.12688/f1000research.2-262.v1 09 May 2014, :262 (doi: ) Latest published: 2 10.12688/f1000research.2-262.v2 v2 Page 1 of 20 F1000Research 2014, 2:262 Last updated: 25 DEC 2016