Incidental Learning and Explicit Knowledge A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Psychology by

It is often assumed that implicit learning of skills based on predictive relationships proceeds independently of awareness. To test this idea, four groups of subjects played a game in which a fast-moving “demon” made a brief appearance at the bottom of the computer screen, then disappeared behind a V-shaped occluder, and finally re-appeared briefly on either the upper-left or upper-right quadrant of the screen. Points were scored by clicking on the demon during the final reappearance phase. Demons differed in several visible characteristics including color, horn height and eye size. For some subjects, horn height perfectly predicted which side the demon would reappear on. For subjects not told the rule, the subset who demonstrated at the end of the experiment that they had spontaneously discovered the rule showed strong evidence of exploiting it by anticipating the demon’s arrival and laying in wait for it. Those who could not verbalize the rule performed no better than a control group for whom the demons moved unpredictably. The implications of this tight linkage between conscious awareness and implicit skill learning are discussed. Introduction A critically important aspect of skill acquisition is learning to take advantage of the various predictive relationships that exist within the relevant domain. Through reinforcement learning and other learning processes, people are assumed to discover and exploit such predictive relationships and to optimize their performance accordingly, achieving greater rewards as their skill grows (e.g., [1]). The question posed in the present article is: do people learn to exploit predictive relationships without showing any conscious awareness of the relationship that they are exploiting? Anyone acquainted with the cognitive psychological literature might suppose that the answer to this question is clearly “yes”. Indeed, there are several well-known lines of research which seem to show beyond any doubt that implicit procedural learning takes place without conscious awareness (see [2], for a review; c.f., [3]). Moreover, in the past 15 years or so, rather little in the way of new research on the topic seems to have been published, possibly suggesting PLOSONE | https://doi.org/10.1371/journal.pone.0179386 June 20, 2017 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 Citation: Tran R, Pashler H (2017) Learning to exploit a hidden predictor in skill acquisition: Tight linkage to conscious awareness. PLoS ONE 12(6): e0179386. https://doi.org/10.1371/journal. pone.0179386 Editor: J Bruce Morton, Western University, CANADA Received: February 16, 2017 Accepted:May 28, 2017 Published: June 20, 2017 Copyright: 2017 Tran, Pashler. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All data are available from the FigShare database: https://doi.org/10. 6084/m9.figshare. 4654783. Funding: This work was supported by the Office of Naval Research (MURI Grant #N00014-10-10072), a collaborative activity grant from the James S. McDonnell Foundation, and the National Science Foundation (Grant SBE-582 0542013 to the UCSD Temporal Dynamics of Learning Center and Grant SES 1461535 to PI: Michael Mozer). The funders had no role in study design, data collection and 17