Variant of the Shepard’s Tabletops Illusion

Site status: If you visited this website in previous two days, you probably noticed we had some serious issues with this site, resulting in most of our icons, images and illusions not showing. This is because most of our images are hosted on Photobucket Pro account, which was down much longer than we expected (due to their system maintenance). Even though we manged to bring everything back up, this made me insecure in future relationship with them. I felt helpless, knowing there isn’t much I can do except wait for the service to come back up. As a result, I’m now positive something has to be done ASAP. As of this Monday, I’m pushing all my energy into migrating this website to more secure, dedicated server with included image hosting, and tracking down best freelance coders and wordpress moguls to help us in the migration process. Now for the illusion…

I know we had bunch of Relative Sizes illusions like this one. Specially Jastrow Illusion and Tabletops. But in my opinion non of them showed the effect strongly as today’s submission did. The image below was created by Lydia Maniatis of American University. Like you presumed, all of the three pink and blue-colored parallelograms are exactly the same. All of the blue lines are equal in length, as well as all of the pink ones are the same. Box B is simply Box C rotated counterclockwise. Why is that all of the three parallelograms look different? Our visual system assumes that the diagonals in A and C are foreshortened and “stretches” them perceptually. The pink lines in B should be foreshortened and stretched, just as they are in C. But our visual system doesn’t stretch a horizontal quite as much as it stretches a diagonal. Why not?

15 Replies to “Variant of the Shepard’s Tabletops Illusion”

  1. This is why, in technical drawing, when you draw a cube, what would be the blue lines in this example are half the length that they should actually be.

  2. oh wow that’s cool! i really like the shapes, and how your brain perceives A and C as foreshortened, and therefore longer. that’s really cool.
    And btw your dedication to this site and it’s visitors is great. i came here yesterday and was upset i couldn’t see all the pictures but I’m glad they’re back up now, and that your pushing for a better server.

  3. Amazing!
    Even though I realized what was going on, I didn’t believe that the third one had the same length until I measured them.

  4. Wow… I can see A & B as the same, but C really looks different! I guess it is the different angle of the box… very cool!

  5. This is really awesome! I didn’t believe it until I checked it in photoshop.

    PS: By the way, thanks for a great site!

  6. I guess its a very good thing that you stop giving these people money for a service they clearly can’t give you.

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