Cats and optical illusions: Now with control experiments!

Last week, I posted about a YouTuber who thinks his he might have tricked his cat with an optical illusion that's based on very human psychology. He asked other people to test the illusion on their cats, just to get some more data points. Now, the psychologists who created the illusion have pitched in to help out, posting a modified version that doesn't elicit the sensation of motion. Show your cat both versions and see whether it's the paper she's trying to kill, or the "rotating" circles. (Thanks to Diana Issidorides!)



  1. egads, Ms Koerth-Baker, you ought to be included as a minor author or at least in the acknowledgements  (…of the resulting paper)

      1.  No, no, no…. true double-blind would require you to tape your eyes shut as well as your cat’s.

        1. That would cause your cat to both attack and not attack the paper until you opened your eyes.

  2. I’ve never actually seen the illusion designed specifically so as not to rotate.  At this stage it is rather unnerving seeing something that clearly looks like it should be moving that isn’t moving.

    Perhaps next we can have a grid of black squares which definitely do not have any grey squares in between them?

  3. Hey, so why does one seem like it’s moving, and the other doesn’t? I tried to discern the difference, but I can’t spot it. Same colors, same orientation. What’s the crucial difference?

    1. rotating:  green white blue.
      Non-rotating:  green white green, blue white blue

      The red/blue one doesn’t rotate for me…

      1. Oh, I see… I was only focused on the outside ring of each circle. Now that you’ve pointed it out, I see the difference. Thanks!

  4. Over the weekend, I tried this using Escher’s “Circle Limit With Butterflies” as a control image. One of my cats ignored both pictures; the other ignored the rotating snakes but was fascinated by the Escher painting:

    Tonight I tried using all three pictures (the illusion, the “official” control, and the Escher painting), and my cats didn’t really react to any of them:

    1. I just tried the circles from the link on my cat. I used the laptop, so he wouldn’t be distracted by paper. He was so unimpressed that it was nearly impossible to keep him in front of the screen, he just didn’t get what I wanted him to do. This is interesting, as he is sometimes distracted by gifs or videos I watch when he is on my lap. He even tried to catch the figure on the screen one or two times. So I would say, he doesn’t notice the optical illusion at all. 

  5. It looks to me that the non-rotating one has radial lines running straight out from the centre, while the lines in the rotating one form spirals away from the centre (in both clockwise and counter-clockwise directions).

    Ah, I see now that this is a result of the offsetting colours. So I would say that it’s not the order of the colours *within* a ring that matters, but the colours shift as you move from ring to ring.

    Edit: This was meant to be a reply to jimkirk above.

  6. Well… I’ve just taken extensive video showing my cat laying on the test and then trying to eat the control. Then she attacked the tiny pieces she ripped off of it. And my other cat tried to attack her by biting her neck during the test.

    Um… hm…

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