You’re going to have to hurry, but if you can get to the Royal Cornwall Museum in Truro, England, before July 3rd, you can see this brilliant sculpture of a dog by British sculptor David Kemp, in his exhibition The Botallack Hoard.  It’s one of the dogs in his piece The Hounds of Geevor, and if you don’t make the show, you can see them anytime in bronze in the centre of the nearby town of Redruth.  Truro and Redruth are in Cornwall, which if you look at a map of England is the pointy bit in the bottom left hand corner.  David lives pretty much as far down the bottom corner as you can go, and I think he’s one of the very best sculptors anywhere working, amongst other interests, on ambiguous images, on which I’ve posted several times before.  He works with every kind of what some people might call junk, but he discovers in it ideas that I find very funny and very beautiful.  If you’d like more information on David Kemp, see his brilliant website.

Here’s another of David’s sculptures, of three musicians, along with more detail of one of them.

Eyespots are fascinating. Nature presents all sorts of camouflage and mimicry, but mostly when prey species look like harmful species, or are camouflaged against background, or imitate leaves, or when seahorses look like seaweed (sea dragons). The imitation then is in 3D, like a waxwork. But eyespots are nature’s only example of patterning that becomes a picture. Eyes in real life tend to be quite rounded and beady or bulging, but butterfly eyespots are flat. Yet they can be amazingly convincing, like the ones at the top of this picture of a peacock butterfly, complete with illusionistic highlights.

And apparently birds really are deceived by the eyes.  A study five years ago by Adrian Vallin and colleagues at Stockholm University demonstrated that butterflies with eyespots covered up really are much more likely to be eaten.  Apparently, the Peacock butterfly tends to rest with wings folded, looking a bit like old leaves, but when threatened suddenly spreads its wings to reveal this alarming mask.  It even makes a noise as well.

But when you look at lots of eyespots it gets more puzzling.  For example, the eyespots that are top in this picture look very realistic, but then the ones lower down are a bit of a mess.  Generally, looking through pictures of lots of eyespots, there’s the same spectrum from very illusionistic to very approximate.  Do they all work in the same way?  And then, the most illusionistic eyespots of all are maybe the ones on the underneath of the wings of the owl butterfly.  But birds only see those when the butterfly has its wings folded, so that only one eyespot is visible.  (Or does the owl butterfly lie on its back with its wings open when it’s depressed?).

So when the birds are frightened by eyespots, are they just responding to a stimulus on the retina that’s a bit like the pattern of stimulus from real eyes, so that even appoximate eyespots will do?  If so, why have some eyespots evolved to be so illusionistic?  Maybe the messy spots, like the ones lower down my photo, are transitional forms.  But if the illusionistic eyespots, complete with highlights, are more effective, can we then say that the birds are being deceived by pictures?  I don’t think there’s another example of a non human unequivocally understanding a picture. Reflections in a mirror, yes.  That was established amongst others by by Frans de Waal of the Yerkes primate research centre in Atlanta. But not pictures. Sure, there’s the the story from ancient Greece, of the contest between the painters Zeuxis and Parrhasius, when the painter Xeuxis painted grapes that were so realistic the birds swooped down to try to eat them? But I don’t believe it. I don’t think animals and birds do understand pictures.

Except maybe of eyespots.

Update January 7th 2010!  Turns out I’m wrong about animals – dogs anyway – and pictures!  Read on for the details.

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You’re welcome to download and use for private purposes any of the imagery on the site, except for a very few pictures where I indicate that third party copyright might apply. But if you’d like a giant, 35 x 23 inch poster, full of illusions, you can buy it (along with loads of illusions on bags, T-shirts etc.) from www.Cafepress.co.uk/optoct. I was delighted when I saw the quality of the poster. Each of the illusions is identified with a discreet caption line, so that you’d be able to follow them up on this or other sites.  And of course, lots of these illusions are brand new versions, often with an extra twist of some kind.

Illusions make brilliant gifts.

You’ll also find a poster of the whole of my optical illusion cartoon story.  If you’d like to preview that, read on.

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This is one of the oldest ambiguous images I know. It’s a small clay mask from Mesapotamia, (in modern day Iraq), made about 3750 years ago. It’s the face of the giant Humbaba, but as he might have appeared to a soothsayer, looking into the writhing entrails of a sacrificed animal for purposes of divination. If the face of Humbaba appeared in the entrails, in the way we sometimes see a face in clouds, it was a sign of revolution on the way. This evocation of the experience is in the British Museum, and they have a web page about it. (They even know the soothsayer who made it …).

I’ve written in earlier posts about the way that artists often seem to use perceptual puzzles as a starting point for aesthetic and emotional effects in artworks. This is a particularly fascinating example. It’s a work of art, but it’s also a record of emotional effect arising out of a perceptual puzzle, an ambiguous image, in a quite different kind of activity – divination. If I’ve got it right, quite a lot of fortune telling starts with ambiguous visual discoveries like this, when peering into tea-leaves, or crystal balls. I wonder how deep the common roots of aesthetics and shamanistic experiences go.

One route you can trace is through the entrails. You can’t quite be sure in this image, but when you look at the real thing, so you can look round the edges, the face is made up of one continuous entrail, coiling to and fro. If you can get to the British Museum, it’s in a case in their new Mesapotamia gallery, but you may have to hunt around, it’s not big.

Here’s a new chance to see illusions as you’ve never seen them before (unless of course you viewed our first post on animated illusion cartoons).

This one is STAG and the SNOW FAIRY.  The illusion it features, on which we have an earlier post, also with an animation, is revolving heads.

You can also view Stag and the Snow Fairy as a
Quicktime Movie

You should also be able to download Stag and the Snow Fairy for mobiles. This is a bit experimental, so please let us know if it works:

formatted (filesize 924 KB, .mp4 format) for
mobiles EXCEPT Iphones

formatted (filesize 3.2 MB, m4v format), for
IPHONES

Here’s another ambiguous severed head illusion.  Is Koala thoughtfully holding up the severed head of Woven Person for inspection, or is it the other way round?  You can see it both ways.  For examples of this illusion in earlier posts, check out The Screams after Munch, the Monks, and the Mask/Skull illusion.  (On that link this illusion may be at the top of the page, if so scroll down for the previous versions).

Does Mercury look like he’s rotating clockwise or anti-clockwise?  That may depend on whether you look at the left hand figure, or the silhouette.  That right hand silhouette figure can appear to rotate either way round.  Some viewers find that it flips from clockwise to anti-clockwise spontaneously, but others may find it hard to make it flip from one rotation to the other at all.  If it doesn’t change easily for you, try waiting till the outstretched arm is pointing top left, and then try to imagine the hand coming towards you (for an anti-clockwise turn) or moving away from you (for a clockwise one).

When the silhouette figure turns clockwise, it’s rotation mirrors the red figure.  When it flips anti-clockwise, the two figures appear to go round the same way, but with the silhouette figure rotating half a turn out of sync with the red figure. I find the change fascinating, like the figures are doing some kind of old style dance, but two different ways.

The rotation of the right hand figure is ambiguous because in silhouette it presents exactly the same image whichever way it turns. Add the reflections and shadows of the red figure and it can only be going one way around.

I made the individual frames for the animation by taking successive still photos all around a reproduction of the original sculpture.  (The original was made by Italian sculptor Giambologna just over four hundred years ago, and is in a museum called the Bargello in Florence, Italy).

There’s something amiss with this dagger, for sure. For a start, the blade’s a bit short. More important, you can’t be sure just from the picture where the blade is pointing. That’s because one and the same perspective view can arise from more than one three-dimensional configuration, out there in the world.  This dagger is particularly hard to interpret.  It could be pointing downwards, with one edge of the blade longer than the other, like the blade in the top left pair of little images, of the dagger seen head on and from the side. Or the edges of the blade could be the same lengths, so we must have a steep perspective view of it leaning sideways, as in the top right hand pair of views. Look at the big image for a few moments, and I think you’ll be able to see it both ways.

Both configurations present exactly the same view in perspective, and both are about equally likely. (Well, maybe equally unlikely with this dagger would be nearer the mark). It’s a variant on an illusion which presents another clash of improbable alternatives – but one that tricks us into going for what may seem the least likely choice.  We could call it the wonky flower box illusion.

Do the flower boxes in this scene look like they’re rectangular, if seen from above, but sloping downwards? But what if they stick straight ahead out from wall, like well-behaved flower boxes should, but are trapezoid, seen from above, (as diagrammed to the right)? Trouble is, once again the perspective view will be the same either way. What’s curious is that in this case, most observers opt for the downward sloping view of rectangular boxes, unlikely though that would be in the real world.  Trapezoid plan boxes just seem too unlikely. It’s a version of the preference for right angles that leads us to accept incredible distortions of size in the Ames Room illusion.  If technical stuff is for you, here’s a serious analysis of the window box effect (though with balconies rather than window boxes doing the weird sloping stuff).  And if you just can’t get enough of that sort of thing, here’s a report of the same illusion in a church (also a bit on the technical side).

Here’s another example of the way illusion effects have been used in decorative art designs. (For examples in earlier posts, check out the category Illusions and Aesthetics, to the right). This mosaic is one of many from the Villa Romana del Casale, in the middle of Sicily, Southern Italy. Only the floors of this Roman villa are left. They are about 1700 years old, and are the largest expanses of mosaic floor surviving from the ancient classical mediterranean world.

The illusion comes in because different shapes in the design tend to pop out from one moment to the next. For example, in the pictures below I’ve selected out a star and a string of lozenges in the picture on the left, and then a hexagon shape in the picture on the right. Note that the hexagon interlocks with the star beside it with no gaps between them or overlaps, but when we select one, the other kind of vanishes, not only in these demo pictures, but even in the big picture at the start of the post. It’s a figure/ground effect, as in the faces/vase illusion, but without the dramatic light/dark contrast of faces and vase.

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On the right, with apologies to Eduard Munch, I’d like to propose an improvement to his famous picture The Scream.  In my version, the screamer really does have something to scream about:  he’s holding up a duplicate of his own head for inspection.  But which head is the one that’s attached to the body, and which is being held up for inspection?  You can make it work both ways, with the upper head looking down on the lower, handheld one;  or, as if the whole figure was leaning over to the right,  with the lower head looking up at the handheld upper head.  It’s another example of the effect in the Mask/Skull illusion, and in Improved artworks no. 1.  I think I invented it, with a hint from Picasso (see the Mask/skull post).  But I’ll be delighted if you prove me wrong by finding an older version. 

No problem about the title for the improved version, it would have to be The Screams.