Another bizarre illusion

I just realized that Matthew must have a thing about fooling vision, for he not only sends us many cases of crypsis (e.g., “spot the nightjar”), but optical illusions as well.

Here’s a good one he sent as a tw**t from Kyle Hill:

Screen Shot 2014-09-08 at 4.18.40 PM

Yes, the lines are abstolutely straight; you can check that out with a ruler or a piece of paper. Now why do they look curved?

Bw45DixCAAAE_dj

41 Comments

  1. Posted September 8, 2014 at 2:28 pm | Permalink

    If you squint so you can no longer see the grey lines, all the black squares in each row seem to be (as they are!) the same hight.

    /@

    • Posted September 8, 2014 at 2:30 pm | Permalink

      Or focus on an individual grey line 🙂

      • Posted September 8, 2014 at 2:37 pm | Permalink

        & if you squint at “hight”, you’ll see that it is actually spelt correctly. 😁

        /@

        • rickflick
          Posted September 8, 2014 at 7:33 pm | Permalink

          I may not be tall enough. But I’ll take your word for it.

  2. Posted September 8, 2014 at 2:31 pm | Permalink

    it takes a half a second, but you can focus on the grey lines and ignore the blocks and they are perfectly straight.

    Optical illusions like this don’t seem to work well for me. Of course, my vision is already so screwed up, it’s almost useless anyway.

  3. Posted September 8, 2014 at 2:37 pm | Permalink

    Yes, our brain does a lot of image processing (or photoshopping). For example, if you close one eye, you see your nose. If you close the other one, you also see your nose. But when you open both eyes, your nose disappears, it is eliminated (photoshopped out) by your brain.

    • Mark Sturtevant
      Posted September 8, 2014 at 8:29 pm | Permalink

      As is your blind spot in the middle of each visual field of the eyes.

  4. Scote
    Posted September 8, 2014 at 2:45 pm | Permalink

    The wavy lines are God 😀

    • gravelinspector-Aidan
      Posted September 9, 2014 at 2:36 pm | Permalink

      The waves being in tribute to the handwaving of Deepakitty?

  5. NewEnglandBob
    Posted September 8, 2014 at 3:01 pm | Permalink

    It is due to the displacement of either color between lines.

  6. Siegfried Gust
    Posted September 8, 2014 at 3:33 pm | Permalink

    Wow, that’s pretty cool. At first I couldn’t believe it. I had to hold a straight edge to the screen to check.

  7. Marella
    Posted September 8, 2014 at 3:39 pm | Permalink

    For me, the area I’m staring at is straight but my peripheral vision has all the lines as wavy.

    • H.H.
      Posted September 8, 2014 at 9:34 pm | Permalink

      Yes, same for me.

    • reasonshark
      Posted September 9, 2014 at 2:13 am | Permalink

      Me too. I wonder if the squares being black and white is significant somehow.

  8. Diana MacPherson
    Posted September 8, 2014 at 4:12 pm | Permalink

    This illusion is completely evil to OCD sufferers.

  9. Gregory Kusnick
    Posted September 8, 2014 at 4:34 pm | Permalink

    Here’s my hypothesis: The gray lines separating adjacent rows are perceived by your peripheral vision as subtracting from the white squares, but adding to the black squares. So the boundary between rows seems to waver up and down.

    But when you look at it directly, your eye correctly perceives the gray as neither white nor black, so the line looks straight.

    • Vin
      Posted September 8, 2014 at 5:35 pm | Permalink

      I’m thinking it has to do with the patterns of white and black vertically and your eye/brain trying to interpret those as continuous lines. I think your brain is trying its best to make a 3D model and is interpreting the varying widths of the black and white as “closer” and “further.” The fact the verticals don’t line up then means it perceives an undulation to try to keep continuity with the verticals. It then tries to make sense of the gray by overlaying onto a topography that doesn’t exist.

    • Andy
      Posted September 8, 2014 at 6:21 pm | Permalink

      I like Greg’s hypothesis, as I started to think along the same lines. But I think it might be wrong. I downloaded the image and processed it a bit to test that idea. If I understand correctly, then that hypothesis suggests that inverting the image should invert the bulges, but it doesn’t (at least to my eye).
      I think that Vin might be right. Your brain tries to interpret the lines of bright and dark squares as low-resolution (pixelated) contour lines on a map and imagines a consistent 3D landscape.
      I tried converting it to different colors (still works but maybe less effective).
      The grey lines seem important; mapping them to black or white reduces the effect. Subtracting a local smoothed background does not eliminate the effect. Running an edge-detection filter definitely reduced/eliminated the effect. Making all the black squares white seems to remove the effect.
      Interesting!

    • Reginald Selkirk
      Posted September 9, 2014 at 6:07 am | Permalink

      It’s demons!

    • John Scanlon, FCD
      Posted September 9, 2014 at 6:54 am | Permalink

      I see it the other way round! – where white and black are adjacent for half the width of a square, it’s the white that seems to bulge at that end, not the black as your description would imply.

  10. Bernie
    Posted September 8, 2014 at 4:51 pm | Permalink

    It seems to me to be akin to a Moire pattern, except that it’s more irregular than the usual examples of that effect.

    Or as my spell checker would have it, a More pattern.

  11. krzysztof1
    Posted September 8, 2014 at 5:29 pm | Permalink

    WHOA!!

  12. trombus
    Posted September 8, 2014 at 7:19 pm | Permalink

    So, I showed this to my 14 year old son and he says “that is called the cafe wall illusion” first documented on the wall of a cafe in Bristol, England. And then proceeds to show me a picture of it in a book about visual illusions. I’m gonna have to amp it up to impress him.

    • Reginald Selkirk
      Posted September 9, 2014 at 6:07 am | Permalink

      A very well-informed 14 year old. You must be proud.

  13. rickflick
    Posted September 8, 2014 at 7:41 pm | Permalink

    I can imagine many scenarios during human evolution which would select for this strange phenomenon. Most of them involve herds of zebras and gently rolling hills of the African savanna. I haven’t yet worked out all the details.

    • John Scanlon, FCD
      Posted September 9, 2014 at 6:55 am | Permalink

      Gently rolling hills of zebras on the dead-flat African savanna.

      • rickflick
        Posted September 9, 2014 at 7:18 am | Permalink

        Right. That would have been late Homo habilis.

    • Posted September 9, 2014 at 12:52 pm | Permalink

      Is there nobody commenting on how absolutely AWESOME this Michael Bach site is? The nec plus ultra on visual illusions?

  14. M Janello
    Posted September 8, 2014 at 7:57 pm | Permalink

    There is an interesting ‘glitch’ in the picture–between rows 6 and 7 the illusion doesn’t apply (for me, anyway), that is, the line between them looks straight. Does everyone else see it this way?

    In those two rows the squares all align, so the illusion must have something to do with the differently-sized squares above and below the grey line.

    • rickflick
      Posted September 8, 2014 at 8:06 pm | Permalink

      For me too. I think it is a clue.

    • ronAnon
      Posted September 8, 2014 at 10:38 pm | Permalink

      I noticed it too. And there the squares touch corner to corner, as they are the same size. The top of the image looks straight too, as the squares seem to be the same size.

      On rows that appear to curve the black and white squares are different sizes causing them so shift somewhat from their adjacent rows.

      It’s maybe the amount of black or white that you see that makes the line seem to curve.

    • ronAnon
      Posted September 8, 2014 at 11:11 pm | Permalink

      Looking closer, the line appears to curve away from the row with a smaller white square toward the row with the larger one.

  15. Mike Leegaard
    Posted September 8, 2014 at 8:04 pm | Permalink

    I’ve been using optical illusions like this to show my dad how easy it is to fool our brains. I haven’t tied this to religion yet. I’m hoping he will make the connection on his own.

  16. Gerald Squelart
    Posted September 8, 2014 at 11:08 pm | Permalink

    We have a whole building looking like this in Melbourne. 🙂
    http://www.trekearth.com/gallery/Oceania/Australia/East/Victoria/Melbourne/photo498715.htm

    • Posted September 8, 2014 at 11:20 pm | Permalink

      I would not like to work in the building opposite!

      /@

      • John Scanlon, FCD
        Posted September 9, 2014 at 6:58 am | Permalink

        Because you’d have to live in Melbourne?
        (It’s the old Syd – Melb thing, can’t resist)

    • infiniteimprobabilit
      Posted September 9, 2014 at 4:53 am | Permalink

      Oz definitely wins the prize for the BIGGEST optical illusion then…

  17. Posted September 9, 2014 at 6:50 am | Permalink

    The previous occupant of a house I lived in in Palo Alto had lined the kitchen drawers in Contact paper something like this. It was sometimes hard to grab just the silverware/cutlery you wanted.

  18. Posted September 9, 2014 at 7:13 am | Permalink

    Matthew Cobb is making my face hurt from all this squinting!

    • NewEnglandBob
      Posted September 9, 2014 at 7:24 am | Permalink

      I know a good ophthalmologist.😜


%d bloggers like this: