August 2023
Volume 23, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2023
Competition between sensory and decisional biases in perceptual decision making
Author Affiliations & Notes
  • Yi Gao
    Georgia Institute of Technology
  • Sixing Chen
    Peking University
  • Dobromir Rahnev
    Georgia Institute of Technology
  • Footnotes
    Acknowledgements  National Institute of Health (awards: R01MH119189) and the Office of Naval Research (award: N00014-20-1-2622)
Journal of Vision August 2023, Vol.23, 5338. doi:
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      Yi Gao, Sixing Chen, Dobromir Rahnev; Competition between sensory and decisional biases in perceptual decision making. Journal of Vision 2023;23(9):5338.

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      © ARVO (1962-2015); The Authors (2016-present)

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Bias in perceptual decision making can have either a sensory or a decisional origin. However, dissociating between these two sources of bias has proven enormously challenging and there are several ongoing debates about whether specific biases are sensory or decisional. In fact, some researchers have gone so far as to challenge the distinction between the two biases. Here, we demonstrate not only that both types of biases exist, but that an experimenter can track the transition from a purely sensory bias to a combination of sensory and decisional biases. Observers saw multiple pairs of peripherally presented faces that induce a strong visual illusion making the faces appear distorted and grotesque. We created images of objectively distorted faces and experimentally introduced them in half of the trials, while in the other half of the trials no faces were objectively distorted. Subjects (N=27) judged whether one of the last two faces had true physical distortion. Initially, subjects classified most faces as distorted as exemplified by a liberal response bias. However, over the course of the experiment, this response bias gradually disappeared despite the fact that the distortion illusion remained equally strong, suggesting that the sensory bias was progressively countered by an opposite decisional bias. This transition was accompanied by an increase in reaction times and a decrease in confidence relative to a condition that does not induce the visual illusion. We replicated all of these results in a second experiment (N=27) where all faces were inverted. These results provide strong evidence that sensory and decisional biases can be distinguished from each other, and suggest that naïve observers may shift from sensory to a mixture of sensory and decisional biases over the course of a standard experiment.


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