1. Neuroscience
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Human observers have optimal introspective access to perceptual processes even for visually masked stimuli

  1. Megan AK Peters  Is a corresponding author
  2. Hakwan Lau
  1. University of California, Los Angeles, United States
Research Article
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Cite this article as: eLife 2015;4:e09651 doi: 10.7554/eLife.09651

Abstract

Many believe that humans can 'perceive unconsciously' -- that for weak stimuli, briefly presented and masked, above-chance discrimination is possible without awareness. Interestingly, an online survey reveals that most experts in the field recognize the lack of convincing evidence for this phenomenon, and yet they persist in this belief. Using a recently-developed bias-free experimental procedure for measuring subjective introspection (confidence), we found no evidence for unconscious perception; participants' behavior matched that of a Bayesian ideal observer, even though the stimuli were visually masked. This surprising finding suggests that the thresholds for subjective awareness and objective discrimination are effectively the same: if objective task performance is above chance, there is likely conscious experience. These findings shed new light on decades-old methodological issues regarding what it takes to consider a neurobiological or behavioral effect to be 'unconscious,' and provide a platform for rigorously investigating unconscious perception in future studies.

Article and author information

Author details

  1. Megan AK Peters

    Department of Psychology, University of California, Los Angeles, Los Angeles, United States
    For correspondence
    meganakpeters@ucla.edu
    Competing interests
    The authors declare that no competing interests exist.
  2. Hakwan Lau

    Department of Psychology, University of California, Los Angeles, Los Angeles, United States
    Competing interests
    The authors declare that no competing interests exist.

Ethics

Human subjects: Twelve subjects (two women, ages 19-32, ten right-handed) gave written informed consent to participate in our behavioral experiments. All subjects had normal or corrected-to-normal eyesight, and wore the same corrective lenses for all sessions, if applicable. Behavioral experiments were conducted in accordance with the Declaration of Helsinki and were approved by the UCLA Institutional Review Board.Eighty-seven respondents replied to our informal online survey. Survey procedures were conducted in accordance with the Declaration of Helsinki and were approved by the UCLA Institutional Review Board.Thus, all survey respondents provided informed consent to participate in the informal online survey, and behavioral subjects provided written informed consent to participate in the behavioral experiments.

Reviewing Editor

  1. Matteo Carandini, University College London, United Kingdom

Publication history

  1. Received: June 24, 2015
  2. Accepted: October 2, 2015
  3. Accepted Manuscript published: October 3, 2015 (version 1)
  4. Version of Record published: February 1, 2016 (version 2)
  5. Version of Record updated: March 31, 2016 (version 3)

Copyright

© 2015, Peters & Lau

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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Further reading

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