A new version of the café wall illusion

by Matthew Cobb

This popped in my tw*tter feed – RT’d by one of my lecturers from 40 years ago, Graham Davey…

I had to stare at this very hard to be sure it was an illusion. Science blogger and lecturer in Psychology, @PeteEtchells, pointed out that it’s a version of the Café Wall illusion. (If you remove the horizontal lines from the graph above, with the exception of the X-axis, you’ll destroy the effect). The illusion was named by the late, great, Richard Gregory, whose book, Eye and Brain is a must-read for anyone interested in such things. (One of my fellow psychology students at Sheffield in the 1970s wrote a whole essay about Gregory’s work, referring to it throughout as ‘Iron Brain’. I guess he hadn’t actually read it…)

Pete pointed my to the relevant Wiki page, which includes this great picture of Gregory next to the original cafe wall where he noticed the effect. This was taken on St Michael’s Hill in Bristol, in February 2010. Gregory died three months later.

Photo by Steven Battle. Taken from here.

9 Comments

  1. GBJames
    Posted November 14, 2016 at 7:25 am | Permalink

    Very cool.

  2. Christopher
    Posted November 14, 2016 at 8:07 am | Permalink

    Never heard of this Café Wall illusion, so forgive the obvious, but does that say “English Meat” in the tiles? Sounds worse than a bit of horse in yer Ikea meatballs.

    • Dominic
      Posted November 16, 2016 at 4:20 am | Permalink

      what’s your beef?!

  3. Posted November 14, 2016 at 8:36 am | Permalink

    That’s what happens when you drop “R”s!

    • Posted November 14, 2016 at 9:58 am | Permalink

      PS – isn’t “English Meat” Benedict Cumberbatch’s nickname?

  4. ploubere
    Posted November 14, 2016 at 10:27 am | Permalink

    Our brains are maladapted to intersecting straight lines if they are at all offset, it seems.

    • Gregory Kusnick
      Posted November 14, 2016 at 11:54 am | Permalink

      “Maladapted” suggests there’s some reproductive penalty to incorrectly perceiving angles in abstract 2D diagrams. I think that’s fairly unlikely.

      More likely the visual system’s adaptive priority is extracting distance and terrain cues from 3D scenes, and this illusion is just a harmless side effect of that.

  5. infiniteimprobabilit
    Posted November 14, 2016 at 7:42 pm | Permalink

    I’ve got both Eye and Brain and its predecessor, The Intelligent Eye.

    Fascinating books!

    It’s a pity R L Gregory did his work before the proliferation of GIF’s and similar easily-promulgated mobile illustrations which can do so much both to generate and to highlight and occasionally explain illusions. I think he would have loved them.

    Btw, that Twitter illusion works for me too, quite strongly.

    cr

  6. ThyroidPlanet
    Posted November 15, 2016 at 2:10 pm | Permalink

    Yes, I liked this! I saw this on MC’s tweet, glad to hear some background.


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