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Alex Holcombe
• Ryo Nakayama


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Psychopy/VisionEgg Installation Notes
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Effects consistent with lower contrast yielding higher latency

  • Hess
  • Pulfrich
  • fluttering hearts
  • anomalous motion
  • Peripheral drift and rotating snakes illusion
  • Contrast-dependent visual-delay illusion (Kitaoka and Ashida 2007)
  • ROUFS, J. A. (1963) Perception lag as a function of stimulus luminance. Vision Res, 3,


  • faster processing of light dots then dark at motion system (M. M. Del Viva, M. Gori, & D. C. Burr, 2006)
  • S-cones slower
    • Our results show that both manual and saccadic responses are slower for S-cone stimuli. Most interestingly, this reaction time difference was twice as large for saccadic responses as for manual responses, suggesting that saccades rely more on the fast signals, not supported by S-cone stimuli, than do manual responses. In a second experiment, our participants performed temporal order judgments on pairs of luminance and S-cone stimuli. Our results show no evidence of perceived time discrepancy between the two signals, which may imply that perceptual judgments utilize different signals from either manual or saccadic responses.(Bompas & Sumner, JoV)
  • What is Collier effect?


Bachmann, Poder, and Luiga (2004)- They had subjects make temporal order judgments on pairs of letters (X and O) presented sequentially in the same spatial location. When the time between stimuli onset was around 50 msec or less, and the second stimulus had less than 1/3 of the contrast of the first stimulus, subjects reliably reported that the second stimulus occurred first. This is the opposite of what would be predicted from differential latencies. It occurred whether the stimuli where light on a dark background or vise versa. The author’s attempts to explain this result were quite speculative, and include hypothesis about ‘driver neurons’ involved in assembling the contents of visual consciousness and a learned bias to assume that more salient flashed stimuli occurred later. -alex white

Other effects proposed to be related to lum and latency

  • Rutschmann, R. (1966). Perception of temporal order and relative visual latency. Science, 152. TOJs to peripheral flashes indicate they're seen up to 70 msec (depending on subject) later than foveal. No attempt was made to equate visibility

Effects on response time

  • Big question is whether lum affects stages beyond perception or is rectified thereafter. Some interesting experiments on this discussed by Jaskowski