Category Archives: Ambiguous images

Hidden Message


Can you read the message encoded in the image?  A few months back I posted about embedding hidden messages in images. Since then I’ve come across a much better way of doing it, using the lettering in the image above.  Lettering? What lettering?  You may not even have been able to spot the lettering yet. I’m not sure who invented it, but it’s brilliant – I just copied the style of lettering from another demo, on the wonderful website of Michael Bach.  It’s clever because to read the message we have not only to achieve a figure/ground reversal, but also because the distracting objects in the picture are seen as if from above (the default view the brain expects), whilst the hidden lettering is seen from below.  So we have to switch two modes of viewing, figure and ground, and also view from above and view from below.  And then I’ve added scene cues to make it even harder.


However there is a way of revealing the message easily – just blur the image, as in the version below.  Without all the distracting detail in the sharp edges in the scene, all that’s required is a figure/ground reversal, and recognisable letters become the most salient features in the image for the brain.



In my first post on this question, I showed a straightforward exchange between the words Truth and Lies with reversal of figure and ground.  I wanted to tweak that, to add the additional reversal between letters seen from above and from below.  To see that ….

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Judith with the Head of Holofernes – or is it the other way round?

Who owns the body?   Judith does to start with, but then Holofernes does, and finally, it’s ambiguous.

Here’s a new addition to our series of ambiguous improved artworks.  Apologies this time are due to Rubens.  I got the idea for these illusions from a print by Picasso.

For a downloadable still of the end of our animation …

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Arcimboldo exhibition in Milan, Italy

Make whatever sacrifice you have to, but unless you were in Washington last Autumn and caught the National Gallery of Art’s exhibition of the work of Arcimboldo there, seize any chance to travel to Milan, Italy, and see it there from January 27th to May 8th 2011.   It’s coming on at the Palazzo Reale. Arcimboldo was born in Milan, but became an unrivalled magician at ambiguous images, working four hundred years ago, mostly at the dazzling court of the Emperor Rudolph in Prague.  This is his painting of Summer, usually in the Louvre in Paris, and one of a set of paintings of the four seasons.

There’s still a movie about Arcimboldo, available in various formats, to the right on the Washington National Gallery’s website for the show, along with details of a huge sculpture that was in the Washington show, of the painting Winter from the same series of the seasons, by film-maker and sculptor Philip Haas.

We know Arcimboldo didn’t invent this kind of image, if only because of a rather naughty example on a 450 year old dish in the Ashmolean Museum.  But he inspired many of the generations of artists, and later psychologists, working with the ambiguous images that you can see in our Ambiguous Images category.

Truth Lies Hidden


A few weeks back the site got a load of US visitors from a link from a discussion on Reddit.  Someone got caught out illegally downloading at college, and as a punishment had to produce a poster about the evils of pirating.  The poster was to be inspected by the authorities and if approved, prominently displayed.  So the reluctant poster artist put out a query:  how can you do a poster that seems to say one thing, but when you look again says something very different. Whatever your take on piracy, (there is a vigorous exchange on the reddit site), the poster problem is an interesting one.  I mean, any of us might need to do a subversive poster someday.  Someone responded that pixelation might be a way to do it, and linked to our pixelation post.

I reckon that would in practice be a really hard way to do it.  Maybe a better way would be by using word combinations that are figure/ground ambiguous, like the Truth/Lies combination shown.  It would still be mighty risky though, if your effort was to be inspected, because it’s hard to tweak the ambiguity just so, leaving the subversive message hidden – but not invisible.  I tried a couple of tweaks above, trying to get a balanced result at top, to push out Truth in the middle, and Lies below.  I haven’t managed to get the recessive message hidden enough yet – not if my freedom depended on it – but maybe you can do better.

Note added at August 3rd 2o11! I’ve come up with a tweaked version of this word pair.  (Scroll down to the bottom of the link).

There are some clever examples of this kind of ambiguity on John Langdon’s site.

David Kemp

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 on a Peacock Butterfly

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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Meet Humbaba


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.

Animated illusion cartoon – post no. 2

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

Koala and Woven Person

Who's looking at who's severed head


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).

A wonky dagger illusion

Wonky dagger illusion

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.

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).