December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
The impact of light level on the Classic and Reverse Pulfrich Effects
Author Affiliations & Notes
  • Victor Rodriguez-Lopez
    Institute of Optics (IO-CSIC), Madrid, Spain
    Department of Psychology, University of Pennsylvania, Philadelphia, PA
  • Carlos Dorronsoro
    Institute of Optics (IO-CSIC), Madrid, Spain
    2EyesVision SL, Madrid, Spain
  • Johannes Burge
    Department of Psychology, University of Pennsylvania, Philadelphia, PA
    Neuroscience Graduate Group, University of Pennsylvania, Philadelphia, PA
    Bioengineering Graduate Group, University of Pennsylvania, Philadelphia, PA
  • Footnotes
    Acknowledgements  VRL was supported by La Caixa Foundation LCF/BQ/DR19/11740032. CD by Health Institute Carlos III PID2020-115191RB-I00. JB by discretionary funds from the University of Pennsylvania. VRL, CD and JB by Spanish government LINKA20122
Journal of Vision December 2022, Vol.22, 3912. doi:
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      Victor Rodriguez-Lopez, Carlos Dorronsoro, Johannes Burge; The impact of light level on the Classic and Reverse Pulfrich Effects. Journal of Vision 2022;22(14):3912.

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

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The Pulfrich Effect is a perceptual illusion that causes the depth misperception of moving objects. Interocular luminance differences cause the Classic Pulfrich Effect (CPE); the darker image is processed more slowly. Interocular blur differences cause the Reverse Pulfrich Effect (RPE); the blurrier image is processed more quickly. A common correction for presbyopia—monovision—has recently been demonstrated to cause the RPE. The effect sizes raise concerns about public safety. But how effect sizes are impacted by light levels (nighttime vs. daytime) is unknown. Here, we report how the CPE and RPE scale with a 60-fold change in light level (250–4cd/m2). Artificial apertures were projected into the pupil plane with a custom 4f optical system. A haploscope presented four grey, interlaced, horizontally moving strips textured with randomly-positioned white bars. Adjacent strips moved in opposite directions at 4 deg/sec. To produce the CPE, interocular differences in light level (75% reduction) were induced by onscreen neutral density filters (OD=0.6). To produce the RPE, interocular differences in defocus blur (3.0D) were induced by voltage-driven optotunable lenses. The resulting interocular processing delays caused the strips to appear in front or behind the screen. Two human observers adjusted the onscreen interocular delays to eliminate the perceived depth such that the strips appeared to move in the plane of the screen. Consistent with previous findings, the CPE increased logarithmically with decreases in light level (Lit, 1949). The RPE also increases with decreases light level, although somewhat more idiosyncratically. The RPE changed similarly to the CPE in one observer. In the other, there was substantially less change. These preliminary results motivate i) analysis of the underlying mechanisms, and ii) a full characterization of how light level interacts with other factors (pupil size, higher-order aberrations) likely to impact the RPE, and hence the perceptual consequences of monovision corrections.


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