Two things today.  First, Amazon UK have 50% off both 59 Seconds and Quirkology!  If you are interested in buying them, the links on the right will take you straight there.

Second, here are two nice illustrations about size perception.  The first is probably the best perspective illusion I have seen….

and the second is a little video that I made yesterday, featuring a classic illusion first created by one of my heroes – Joseph Jastrow….

You can download a template to make your own version of the second illusion here.

Which is your favourite?


    1. The three cars are the same size, measure them if you must I find it easier to relax my vision and focus on them slightly cross-eyed. They are exactly the same size.

  1. The second, because I printed one of these off and showed my kids yesterday and they think that I’m some sort of wizard.

  2. Aargh! Too early for me to be this confused! Both very cool, but as I’m excited at possibility of never ending line of identical cars that appear to get smaller n smaller. Like vehicular Russian dolls…but they’re just full of themselves!

    1. That’s kind of the point. There’s three identical pictures of a car that were projected onto the picture of a street, but because of their location, our brain tells us that they get smaller.

  3. I have seen loads of these type of perspective illusions & usually have no problem convincing myself that despite my perception the objects are indeed the same size, but these two have seriously f-ed my brain!!! Going for a lie-down in a darkened room….

  4. there is a real life perspective illusion where I work. In the garden is a stream that runs uphill and wherever your viewpoint, it looks as if it is going uphill. Only by closing your eyes and walking alongside it can you be sure that the slope is actually slightly the other way. I have tried for months to figure out how it is doen but I am still struggling with it. Also I have got my feet wet once or twice…

    1. There’s a raodside attraction near where I used to live in New Brunswick, Canada called Magnetic Hill that has a very similar illusion on a bigger scale, you can drive your car down to the ‘bottom’ of a slite hill (more like a slight grade) put it into neutral and coast back ‘uphill’! It’s quite a powerful illusion.

    2. I wish I wouldn’t answer posts while tired… I meant to say “roadside attraction” !

      And I spelled “slight’ incorrectly the first time too!

      Sheesh. Must have been the illusions addling my brain!

  5. I find that, with the first one, if you tilt your head so that your eyes are parallel with the slope of the cars then the effect disappears and they look the same size.

  6. No can’t get my brain to work properly with the first picture, it hurts.
    I think the second illusion is cool very simple but effective.
    Well done.

  7. Okay, I have been at the first pic with my ruler and I can see using that they are all the same size but it doesn’t matter whether I tilt my head, cross my eyes or mask out bits of the photo my brain tells me that they are all different – aaarrrgh!!!!

  8. The first picture is very cool. The best perpective illusion I’ve seen.
    The film won’t play on my rubbish signal but sure it’s just as good. 🙂

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