What is it like to be a cat?

There are few ways to enter the consciousness of another species, much less another human, but at least we can see if some animals process visual information the way we do. I am speaking in particular of visual illusions, like the “rotating snake” illusion that obviously has deceived this felid:

Of course there’s no control (does this cat scratch at any image?), but I suspect it sees the snakes rotating, just as we do when we look at this:


If you let your gaze wander over it, it moves, but if you fix your gaze on one section, it stops.  It’s quite an illusion.

You can print it out from above or here (the site also has information about the illusion). I would of course be immensely pleased if some readers would test their cat and report back about whether it seems to perceive movement.

h/t: SGM. Alejandro


  1. Matthew Cobb
    Posted March 7, 2013 at 12:58 pm | Permalink

    That’s great and I’ll use this next year (I already show the snake illusion). But, of course, this doesn’t necessarily tell us anything about consciousness, simply that the cat’s visual system and ours are wired up in a similar way. Wield Occam’s razor!

    • steve
      Posted March 7, 2013 at 1:20 pm | Permalink

      Unless every little fact about the way we perceive things, added together, makes up consciousness. If that were the case, and it is, then this would tell us a little about consciousness!

      • Launcher
        Posted March 7, 2013 at 3:26 pm | Permalink

        I like to think of any animal brain as continuously performing two simple yet critical functions: 1) processing sensory information and 2) forming a motor plan that acts on that information. Sure, for us humans there’s a lot of stuff that goes on between 1 and 2. But the result of all that internal pondering, which we call “consciousness”, is really just us thinking about what action we WILL do or COULD do at some point in the future.

        So I agree with Steve on that point, with the addition that it’s a combination of perception AND action (overt or not) that underpins consciousness.

        As for the cat, many of you may already know that the feline visual system is probably THE most studied neural system in mammals. From my postdoc days, I recall this paper from Yang Dan at Berkeley:

        “Asymmetry in visual cortical circuits underlying motion-induced perceptual mislocalization.” J Neuroscience. 2004.

        Among other things, it suggests a neural mechanism for the so-called “waterfall illusion”, or motion aftereffect, based on recordings from single units in the cat primary visual cortex. Physiological studies like this one, as well as behavioral studies, suggest that illusions and other aspects of the visual system are very similar across species.

        • steve
          Posted March 7, 2013 at 5:14 pm | Permalink

          I would say that perception is a kind of action. If you wanted to divide information cleanly into input and output categories, you could divide it into sensation and action. But once you get inside the brain, that division loses meaning. I don’t melt all these terms together just to make it look like I’m still right (but certainly that’s a concern). I’m just saying that that when someone says, “Yeah, here’s something the brain does, but it’s not *really* consciousness,” they are unwittingly espousing some form of vitalism. These little things the brain does really are little parts of consciousness, just like “microevolution” is a little part of “macroevolution”. The *real* consciousness they’re holding out for is magic.

          Even outside the brain, there are feedback loops that blur the line between sensation and action. For example, this circley snake illusion depends on you moving your eyes. That’s action. Thwarting it depends on you concentrating really hard to not move your eyes. More action.

        • Launcher
          Posted March 7, 2013 at 6:04 pm | Permalink

          All good points – I’m definitely behind your point about different aspects of brain function blurring into each other. My hasty division of brain processes into input and output comes from how non-cognitive (as usually defined) systems-level neuroscience is often practiced: sensory and motor functions are studied as separate components. There are historical reasons for this, given the anatomical separation of sensory systems as well as the ease of studying sensory systems in anesthetized animals (my line of work).

          But you’re totally right about feedback loops, and so-called “sensory-motor” regions of the brain give ample evidence of how our nervous system reacts to external stimuli. The saccadic eye movement system, mediated to a large extent by brainstem nuclei, is a prime example that’s also very relevant to the illusion at hand. Indeed, there are no “pure sensory” neural systems, as the processing of sensory input is such that it evokes – and is altered by – attentional mechanisms in a continual loop of bottom-up (brainstem-to-cortex) and top-down processing.

          It goes without saying that all of this feedback-loop action of the brain occurs in all animals with a nervous system, cat or human or, yes, dog. And it’s all a consequence of our being animals that have to eat.

    • Notagod
      Posted March 7, 2013 at 9:37 pm | Permalink

      Does that mean the analysis could be applied the other way around? Can we claim that the illusion isn’t necessarily a part of human consciousness? If we camouflaged the illusion within a set of moving machinery would the human consciousness think that the circles were really moving? If so, would that be different from what the cat might be perceiving since it doesn’t understand the properties of paper?

  2. gbjames
    Posted March 7, 2013 at 1:03 pm | Permalink

    Do cats see color?

    • Reginald Selkirk
      Posted March 7, 2013 at 1:21 pm | Permalink

      According to this expert source (i.e. first link I found in Google)
      Kitty Show
      Cats responded to the colors purple, blue, green and yellow range. Red, orange and brown colors appear to fall outside cats color range, and are most likely seen as dark to mid shades of gray. Cats appear to see less saturation in colors than do humans, meaning cats do not see colors as intensely or vibrantly. Purple, blue & green appear to be the strongest colors perceived by cats

    • Launcher
      Posted March 7, 2013 at 3:35 pm | Permalink

      Cats are dichromats, meaning the photosensors in their retinas are sensitive to two different (and overlapping) ranges of light frequencies. They can distinguish many colors, but will mix up some that a trichromat (like a normal human observer) would not.

      Now, consider that many bird species have four types of photoreceptors. They can actually distinguish color mixtures in the visible range that we can’t, and also see into the ultraviolet range.

      • Reginald Selkirk
        Posted March 8, 2013 at 8:14 am | Permalink

        When it comes to visual spectrum, mantis shrimp rule.

      • michaelbusch
        Posted March 9, 2013 at 2:22 pm | Permalink

        If Wikipedia is correct, there are some human tetrachromats. Of course, their photopigments respond differently than those of the birds.

  3. Flo M
    Posted March 7, 2013 at 1:06 pm | Permalink

    OMG, your post’s title is a play on a book by Thomas Nagel, who lost it as you and Allen nicely pointed out recently….

  4. Bobbie Harley
    Posted March 7, 2013 at 1:07 pm | Permalink

    Unfortunately, there is another explanation for visual processing: not just “does it perceive” but also “does it care” about movement in general? My friend Katan (that’s Hebrew too) is too dumb to care (or maybe too elderly)

    Bobbie Harley

  5. Stackpole
    Posted March 7, 2013 at 1:10 pm | Permalink

    Nothing rotates for me.

    Does that mean I am secretly (and unconsciously) a d*g lover?

    • Veroxitatis
      Posted March 7, 2013 at 2:02 pm | Permalink

      It means you are too cer(e)b(e)r(us)al.

    • Marella
      Posted March 7, 2013 at 2:55 pm | Permalink

      It probably means you should go and have your eyes checked. Srsly.

    • Launcher
      Posted March 7, 2013 at 3:40 pm | Permalink

      You may have an undiagnosed nystagmus or other eye-movement disorder!


    • JohnnieCanuck
      Posted March 7, 2013 at 9:33 pm | Permalink

      I followed the link in the OP where I found that the effect varies substantially between subjects.

      He goes to some pains to point out that susceptibility to the illusion doesn’t correspond to stress levels nor to criminal tendencies. G*d lovers may or may not find this stressful.

      You can stop worrying, you are perfectly normal. For some definitions of normal, at least.

    • Diane G.
      Posted March 9, 2013 at 8:28 pm | Permalink

      Doesn’t rotate for me either.

  6. nickswearsky
    Posted March 7, 2013 at 1:13 pm | Permalink

    That is SO cool!

  7. ChrisKG
    Posted March 7, 2013 at 1:16 pm | Permalink

    I can think of an experiment for this. I have a one-eyed cat that can be used to determine if the illusion works with only one eye. I have another cat with normal binocular vision so testing each cat will determine if the monocular cat can see the same illusion.

    • Posted March 7, 2013 at 1:26 pm | Permalink

      The illusion works for me [a human] with one eye or two eyes open

      I’m going to see if colour is essential to the illusion for me by printing in monochrome. Will report back.

      • Posted March 7, 2013 at 1:35 pm | Permalink

        1] Monochrome version still works, but not so much motion ~ more stately
        2] Increasing the amount of white border around the monochrome version increases the illusion strength to a degree, but still it’s more sedate than the original

        • JohnnieCanuck
          Posted March 7, 2013 at 9:35 pm | Permalink

          Follow the link in the post to learn more about what has been discovered wrt monochrome and background shading.

    • marlonrh
      Posted March 7, 2013 at 1:29 pm | Permalink

      Well, I am a one-eyed person, and the illusion does not work for me.

      • ChrisKG
        Posted March 7, 2013 at 1:39 pm | Permalink

        Hmm. Interesting. Any idea how to tell if this will work for a cat? I will have to work under the assumption that cat vision is not identical to human vision as noted elsewhere on this thread.

      • Launcher
        Posted March 7, 2013 at 3:44 pm | Permalink

        Cat vision isn’t identical to human vision, but it’s very close. Cats do have lower spatial acuity, which could affect the salience of the rotating illusion. But if the illusion is driven by slow eye drifts or microsaccades (see my link in a comment above), then even poor visual acuity should probably still activate the illusion because the gratings have both fine and coarse components.

      • Posted March 8, 2013 at 9:18 am | Permalink

        I am a two-eyed person, and the illusion works well for me — if I cover one eye, I still see motion, but it is somewhat reduced.

  8. Marcoli
    Posted March 7, 2013 at 1:24 pm | Permalink

    Ah, yes, this web site. I often show this site to my kids and their friends.

    • Marcoli
      Posted March 7, 2013 at 1:24 pm | Permalink

      I am now inspired to try it on my dog.

  9. SmoledMan
    Posted March 7, 2013 at 1:27 pm | Permalink

    God wanted it this way.

  10. BillyJoe
    Posted March 7, 2013 at 1:50 pm | Permalink

    What friggin’ snake?

    • Flaffer
      Posted March 7, 2013 at 2:21 pm | Permalink

      Snake refers to the motion as it circles the edges.

  11. Posted March 7, 2013 at 2:05 pm | Permalink

    I am so testing this on my dog. But he’ll probably eat it.

  12. Posted March 7, 2013 at 3:12 pm | Permalink

    I can report that both cats saw a piece of paper and tested its flavors and that the dog sat and stared at it for a good minute before deciding the window was a cooler place to be.

  13. Ougaseon
    Posted March 7, 2013 at 3:22 pm | Permalink

    The strength of the effect depends a great deal on pupil size, ultimately disappearing entirely through a pinhole, which suggests that it isn’t neural. Wide open pupils introduce optical aberrations into the retinal image, and these aberrations also change with focal state, which is constantly fluctuating. Dynamic aberrations could cause apparent motion in carefully constructed stimuli like this one. A pinhole pupil effectively removes these aberrations, eliminating the effect.

    By the way, if this is true the strength of the effect will probably decrease with age, since your lens hardens and can’t deform as much, meaning those focus fluctuations are reduced, and your daylight pupil size tends to decrease!

    Of course the real way to test this would be to use an adaptive optics system to correct for aberrations in a person with a dilated pupils and see if the effect goes away.


    • Launcher
      Posted March 7, 2013 at 3:46 pm | Permalink

      > “ultimately disappearing entirely through a pinhole”

      That makes sense, as the illusion appears to be driven by minute eye movements. (See my link above.)

    • Pete Taylor
      Posted March 8, 2013 at 4:19 am | Permalink

      Well, I’ve had cataract operations in both eyes and have small plastic lenses embedded, and the illusion works for me.

      This suggests the effect is not depending on lens fluctuations.

      • Pete Taylor
        Posted March 8, 2013 at 4:20 am | Permalink

        depending = dependent

  14. gluonspring
    Posted March 7, 2013 at 3:37 pm | Permalink

    Completely unable to get my cat to even look at the paper. I tap on the paper, it maintains eye contact with me. I leave the paper at it’s feet, it walks away without glancing at it.

    For me, the illusion is MUCH stronger on the computer screen. Perhaps someone should test their cat with an iPad…

    • Posted March 7, 2013 at 5:38 pm | Permalink

      I printed it out to take to Skeptics in the Pub and found the print version is weaker. Are the colours germane? Does chromatic aberration play a part? If pupil size plays a part then the illusion should be stronger in dim light.

      I notice that the movement disappears in the circle I am looking at directly – it seems to be an “out-of-the-corner-of-your-eye” effect.

  15. couchloc
    Posted March 7, 2013 at 7:09 pm | Permalink

    Thanks for this interesting post. It may be useful to note that understanding the nature of “visual awareness” (as interesting as it is) is not really the same issue as understanding “consciousness” as Nagel and others are concerned with. Some of the comments here appear to be hinting that these are the same sort of thing. The point can be made without appealing to anything Nagel says himself. Here, for instance, is scientists Crick and Koch’s response to the problem of consciousness that suggests there are different phenomena involved in the two cases being mentioned:

    “Well, let’s first forget about the really difficult aspects, like subjective feelings [i.e., consciousness], for they may not have a scientific solution. The subjective state of play, of pain, of pleasure, of seeing blue, of smelling a rose -– there seems to be a huge jump between the materialistic level, of explaining molecules and neurons, and the subjective level. Let’s focus on things that are easier to study – like visual awareness…..” (“What is Consciousness”, Discover, November 1992, p. 96.)

  16. Posted March 7, 2013 at 7:14 pm | Permalink

    I have tried to look at the whole picture and yes, I saw the rotating snake. But then I blocked all of the images and only left 1 to look at, the snake didn’t move ;). How can I explain this?

  17. Posted March 7, 2013 at 7:40 pm | Permalink

    I’d love to test it out, but my Fattee Cattee does that to paper regardless of the printed word, the illustrated dragon or a page of illusory slithery coiling snakes!

  18. Marcoli
    Posted March 7, 2013 at 8:18 pm | Permalink

    OK, I tried it on my dog. He looked at the screen when I tapped it, looked at me for clarification, looked at the screen when I tapped it again, then shrugged and walked away. Dogs have fewer illusions than cats.

    • John Scanlon, FCD
      Posted March 8, 2013 at 10:04 am | Permalink

      Fewer neurons.

    • Launcher
      Posted March 8, 2013 at 11:36 am | Permalink

      The right control would be to show your dog a movie with actual rotating elements. He probably won’t look at that either! (My cat in all likelihood would act equally indifferent to anything that doesn’t look like swimming fish.)

      • ChrisKG
        Posted March 8, 2013 at 11:39 am | Permalink

        So, can we assume that cats hunt visually and dogs by smell? Therefore, we are comparing apples and oranges.

  19. haggholm
    Posted March 7, 2013 at 9:17 pm | Permalink

    Enlist your readership! Post links to a test[1] and control[2] image and collect some data!

    [1] Test: http://www.psy.ritsumei.ac.jp/~akitaoka/rotsnakesstrong6b2013-test.jpg

    [2] Control: http://www.psy.ritsumei.ac.jp/~akitaoka/rotsnakesstrong6b2013-control.jpg

    I would do this, but do not have the necessary access to cats.

    • Marcoli
      Posted March 8, 2013 at 5:16 am | Permalink

      Test image is writhing snakes. Control image, which to me looks like the test image, does not move. How is it that the control image does not move? What is this magic!!??

      • John Scanlon, FCD
        Posted March 8, 2013 at 10:27 am | Permalink

        They differ in the order of colours around each circle. Where the blue and yellow strictly alternate (occurring either before or after black as you go clockwise on any circle, but not both) they are perceived in the peripheral field as effects of rotation ‘during’ saccades, i.e. between fixations. Where the order varies (a given colour can be on either side of the black in any circle) there is no consistent resemblance to a motion-blur effect, so no illusion.

        This illusion of motion is a kind of inverse of ‘flicker-fusion’, something that has been proposed as the primary function of strong banding patterns on certain real snakes such as the corals Micrurus and their mimics – mentioned recently on this site in connection with A.R. Wallace, in a comment by coral (and rattle-) snake enthusiast Harry Greene. When a snake of nearly uniform body diameter and bold regular bands slides by, especially in low light where your retina loses temporal precision, it can really appear to be stationary or moving backwards (so its location can’t be predicted accurately over short timescales). A bit like the wagon-wheel illusion in old movies.

    • gbjames
      Posted March 8, 2013 at 5:51 am | Permalink

      Now, that is cool!

  20. ophu
    Posted March 7, 2013 at 10:22 pm | Permalink

    I just can’t see it. And it gave me a headache.

  21. Posted March 8, 2013 at 3:32 am | Permalink

    will try it with my kitties and see how it works here in Burundi, s. hemisphere…

  22. Posted March 8, 2013 at 9:20 am | Permalink

    Note that the person who posted the video on YouTube also wrote this:

    Can cats experience visual illusions? Show your cat the rotating snakes illusion (available here: http://www.ritsumei.ac.jp/~akitaoka/i…), film it and let me know the result by filling in this form:


    If enough people do this we might be able to crowdsource some real evidence that cats can see visual illusions!

    • Launcher
      Posted March 8, 2013 at 11:41 am | Permalink

      No matter the massive corpus of psychophysical studies on cat visual perception spanning 8+ decades.

  23. Fastlane
    Posted March 8, 2013 at 12:20 pm | Permalink

    I just found a new way to entertain my kitteh. 😀

  24. gravelinspector-Aidan
    Posted March 8, 2013 at 4:42 pm | Permalink

    OK ; where can I get the wallpaper?
    The wife has given me permission to decorate one wall of what I’m being relegated to as a “study”. I need that wallpaper!
    Or I could use it for doing the ceiling, for when the room gets doubled up as a spare bedroom.

    • Posted March 9, 2013 at 7:37 am | Permalink

      Digital custom UV-resistant inkjet printing onto wallpaper is big biz these days for restaurants, nightclubs, libraries, exhibition spaces etc.

      There are plenty of outfits who will print this for you onto rolls in such a way that the pattern repeats seamlessly at the joints.
      Just Google “custom wallpaper for walls” ~ prices are around £30/m^2 in the UK.

      You need only upload a suitably sized image file & then they contact you to discuss details.

      This revolving snake image is almost tile-able with some cropping:- http://img.gawkerassets.com/img/18dn2gj5hxheijpg/original.jpg
      I put the above image fullscreen on my monitor & the snakes stopped rotating when viewed beyond around 1.5m on my 0.53m wide screen. Thus I suppose you would need to scale up the image elements by a factor of 2 or 3 to be effective on say a ceiling. Beyond a factor of 3 the colour edges are too pixelated & would require smoothing.

      I can email you a suitable cropped “tile” at 200%, 300% & 400% & you could print out say 16 of each to experiment with. I wonder if a large expanse of the image would work because the strength of the effect seems to depend on the white border [according to the “experts”, but I’m not convinced] My email address is in my name-link.

      The pattern reminds me of awful ’70’s wallpaper. Your wife is very tolerant… 🙂

      • gravelinspector-Aidan
        Posted March 9, 2013 at 3:29 pm | Permalink

        My wife hasn’t seen it yet to be tolerant. (I’m offshore).
        After posting, I remembered that we’ve got several 1m+ swath roll-fed inkjet printers at work. It’s really just a case of finding images, and then printing chunks off on the tail ends of rolls as they come available. I’m sure I’ll be able to find someone in the office who appreciates my sense of humour to actually fire the machine up on a Friday afternoon.

  25. Brian Vroman
    Posted March 8, 2013 at 9:27 pm | Permalink

    I know nothing about the science of cats. All I can say is that when I printed this off and tried to get my two cats interested, the only thing they wanted to do is sit on it.

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