This stimulus consists of a pair of band-pass filtered white noise components moving in opposite directions and that are spatially modulated with out of phase sinusoidal modulators perpendicular to the direction of motion. It is used to study psychophysically the human sensitivity to motion gradients and the nature of the local and global motion integration stages.

References:

  Watson & Eckert (1994) Motion-Contrast Sensitivity: Visibility of Motion Gradients of Various Spatial Frequencies. Journal of the Optical Society of America A 11(2), 496–505

  Meso & Hess (2010) Visual motion gradient sensitivity shows scale invariant spatial frequency and speed tuning properties. Vision Research 50(15):1475–1485

  Meso & Hess (2011) Orientation gradient detection exhibits variable coupling between first- and second-stage filtering mechanisms. Journal of the Optical Society of America A 28(8):1721–1731

  Meso & Hess (2011) A visual field dependent architecture for second order motion processing. Neuroscience Letters 503(2):77–82

  Meso & Hess (2012) Evidence for multiple extra-striate mechanisms behind perception of visual motion gradients. Vision Research 64:42–48

Here is the math behind this stimulus:

  c1 = pnoise(x/15,y/15+3*speed*time)
  c2 = pnoise(x/45,y/45-speed*time)
  m1 = sqrt(0.5*(1+m*sin(2*pi*fm*y)/100))
  m2 = sqrt(1-m1*m1)
  z = c1*m1+c2*m2

The whole stimulus is generated in real-time using a GLSL shader that runs right inside your WebGL-compatible browser. The plain Math behind the stimulus was converted to this optimized GLSL shader using the new Psykinematix Pro Edition. Translation to Matlab and Python code is also possible !

This whole widget was also fully generated using Psykinematix Pro Edition. The parameters that control the stimulus properties through the sliders are the same as the ones you would define as dependent or independent variables when using the stimulus in an actual psychophysical experiment run in Psykinematix. The widget creation is otherwise fully customizable with your own logo, copyright, links, etc.

To learn more about the widget creation, click on the above "Made With" button !