Kaleidoscopic Motion Illusion

What I’m about to show you proves that there are still new optical illusions out there, just waiting to be discovered by some brave soul! On your right you may see a rotating wheel that seems to pulsate each time it aligns with the inner, star-shaped stationary object. You may also have noticed, that at the same time, the inner stationary shape seems to wiggle when the alignment occurs. Why is this happening, when it’s obvious that the inner shape is stationary, while the outer wheel’s rotation is perfectly smooth?

It turns out that the pulsations is caused by color assimilation, and the wiggling happens due to “ambiguous figure-ground segregation” (whatever this means), as Peter van der Helm discusses in his paper (2007).

26 Replies to “Kaleidoscopic Motion Illusion”

  1. Figure-ground is how we tell what is the background and what is the object in front of it. So I’m guessing “ambiguous figure-ground segregation” means in the split second that the two shapes align our mind gets confused as to which circle is the background and which is the foreground that to us it looks like they ‘pulse.’

    This makes sense to me.

    But, first time I’m seeing this illusion, and it’s very cool! :D

    1. I agree with Sam and Xaio. If you use your hand to cover everything except a portion of the outer wheel, you can clearly see it pulse. Good effect though.

    2. It does, but at a much higher frequency than than the perceived pulse that occurs due to the illusion. There is also a longer pause at the begining of the rotation, but again, this does not contribute to the overall illusion, as it doesn’g happen at every crossing. Take another look and see if you agree.

    3. I totally doesn’t, but even if you leave, like, one pixel of the blue star uncovered, the optical illusion remains

  2. Actually the movement of the outer wheel is not completely smooth. You can check it by hiding all the picture except for the top. Looks as if there is one frame missing in the animation…

  3. Also the rim of the dark blue star (particularly between 10 and 3 o’clock) turns darker when the red wheel intersects with it. I think this why one experience the dark blue star to wiggle.

  4. The outer red shape does skip a bit (not completely smooth animation). However, I rebuilt it myself with completely smooth animation and the blue shape inside still appears to jump.

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