Mind Tricks #1

1. We certainly all agree that on the right side a wheel is seen rotating.
   
2. On pressing the “ show ” button, a brown picket fence (a palisade) will fade in. When it is fully opaque, it largely occludes the rotating wheel, but one can still perceive its rotation.
   
3. On pressing the “ move ” button, the palisade begins to, well, move.
   
4. What do the spokes of wheel look like now? A little distorted, similar to the icon on the top right?
   Yes, it is somewhat difficult to perceive this, due to the timing distortions (“anti-aliasing”) by computer presentation.
   
5. When fading out the palisade, the distortion vanishes as soon as a little of the wheel becomes visible through the semi-transparent palisade.
   
6. The effect changes drastically when changing the relative speeds.