As both the midget in the country of Brobdingnag and the giant on the island of Lilliput, Lemuel Gulliver—the protagonist of Jonathan Swift's Gulliver's Travels—experienced firsthand that size is relative. As we cast a neuroscientific light on this classic book, it seems clear to us that Swift, a satirist, essayist and poet, knew a few things about the mind, too. Absolute size is meaningless to our brain: we gauge size by context. The same medium-sized circle will appear smaller when surrounded by large circles and bigger when surrounded by tiny ones, a phenomenon discovered by German psychologist Hermann Ebbinghaus. Social and psychological context also causes us to misperceive size. Recent research shows that spiders appear larger to people who suffer from arachnophobia than to those who are unafraid of bugs and that men holding weapons seem taller and stronger than men who are holding tools. In this article, we present a collection of illusions that will expand your horizons and shrink your confidence in what is real. Try them out for size!

Small Change

Do you see tiny objects photographed with a macro lens? Look again. This remarkable illusion combines tilt-shift photography—in which the photographer uses selective focus and a special lens or tilted shot angle to make regular objects look toy-sized—with the strategic placement of a giant coin. Art designers Theo Tveterås and Lars Marcus Vedeler, from the Skrekkøgle group, created the enormous 50-cent euro coin from painted and lacquered wood at a 20:1 scale.

Barbie Trashes Her Dream House

At first sight, they look like real-life scenes from the television show Hoarders, precleanup. In reality, they are photographs of 1:6 scale dioramas by St. Louis–born artist Carrie M. Becker. She makes the cardboard boxes, garbage bags and other trash herself. The furniture and tiny objects are from Barbie's dream house and a Japanese miniatures company called Re-Ment. Becker filths up the rooms with actual dirt collected from the filter of a DustBuster, using the occasional Re-Ment meatball to simulate dog poop on the floor. When she photographs the scenes without an external reference, our brain relies on our everyday experience and assumes that the minuscule objects are life size. Only in proximity to an extraneous, actual-size object does the illusion fail.

Supersize Me

You can look 10 pounds thinner with a well-known slimming trick: vertical lines elongate your shape and give you a more svelte appearance, right? Wrong! Vision scientists Peter Thompson and Kyriaki Mikellidou of the University of York in England say instead that it is time to ditch your vertical-striped wardrobe and invest in some horizontal-striped outfits. They found that vertical stripes on clothing make the wearer appear fatter and shorter than horizontal stripes do. Notice that the vertical-striped lady seems to have wider hips than the horizontal-striped model in the accompanying cartoons. The phenomenon is based on the Helmholtz illusion, in which a square made up of horizontal lines appears to be taller and narrower than an identical square made of vertical lines. The original report from 1867 of this illusion contained the intriguing reflection that ladies' frocks with horizontal stripes make the figure look taller. Because the remark ran counter to contemporary popular belief, the York researchers decided to put it to the test, finding that 19th-century German physicist and physician Hermann von Helmholtz did indeed have a great eye for fashion.

Full Moon

The full moon rising on the horizon appears to be massive. Hours later, when the moon is high overhead, it looks much smaller. Yet the disk that falls on your retina is not smaller for the overhead moon than it is for the rising moon. So why does the overhead moon seem smaller? One answer is that your brain infers the larger size of the rising moon because you see it next to trees, hills or other objects on the horizon. Your brain literally enlarges the moon to fit the context. Look for this effect the next time you see the moon in real life.

17 Comments

1. 1. maxw3st 09:57 AM 7/21/12

   This article on size illusions would work much better if you included the photos the article refers too.

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2. 2. promytius 11:17 AM 7/21/12

   This piece of fluff is all over the place; verbal salad, with NO pictures - hello? You make no sense of the timelines for research and explorations in this area, no attention to the evolution of understanding of illusions, and a chaotic approach to sequencing. You have given the illusion of a logical article.

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3. 3. Richieo 12:15 PM 7/21/12

   The full moon rising on the horizon appears to be massive. Hours later, when the moon is high overhead, it looks much smaller. Yet the disk that falls on your retina is not smaller for the overhead moon than it is for the rising moon. So why does the overhead moon seem smaller?
   
   The sun does it too, I was taught it the atmosphere acting as a lens, which is somewhat thicker viewed at an oblique angle, ie. dawn and dusk...
   
   I always see larger disks at these times, even without a cluttered foreground....
   
   So I totally disagree with the above statement in this article...
   

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4. 4. Richieo 12:20 PM 7/21/12

   The full moon rising on the horizon appears to be massive. Hours later, when the moon is high overhead, it looks much smaller. Yet the disk that falls on your retina is not smaller for the overhead moon than it is for the rising moon. So why does the overhead moon seem smaller?
   
   The sun does it too, I was taught it is the atmosphere acting as a lens, which is somewhat thicker viewed at an oblique angle, ie. dawn and dusk...
   
   I always see larger disks at these times, even without a cluttered foreground, ie. sun/moon rise/set over the sea...
   
   So I totally disagree with the above statement in this article...
   

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5. 5. Rev.Corvette 02:36 PM 7/21/12

   Cheap shot Scientific American....(the pictures?)

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6. 6. rwormus 05:19 PM 7/21/12

   Excerpts from my published paper, might make 'tricking the mind' seem superfluous!!!
   
   The evolutionary process has created an aggressive territorial human animal with a highly evolved brain, capable of 'fabricating' its own intuitive-based reality; and incapable of counter-intuitive arguments.Analogous to the maternal instinct, the human mind, then, protects it’s ‘illusion’ of reality by deploying an armory, the Human Psyche's insurmountably powerful defense mechanisms; first, and most formidable, denial and then, as necessary, rationalization, repression, regression, and dissociation, affectively closing off Man’s mind to the external input of alternate counter-intuitive realities, concepts, or change. Recent research in neuroscience has irrefutably proven that the mind actually augments crude two-dimensional, blurred afferent images, sounds, smells, and context clues into the sharp, clear, crisp ‘illusion’ of the intuitive external reality mankind takes for granted. Like an artist, it does this by cleverly adding form, dimensionality, animation, colorization, and shadowing; virtually fabricating an experientially-based version of an external reality.
   This synthesized illusion of reality (a hologram in effect) has been well documented in the scientific community. The universality, or ‘conserved parity’, between humans of like realities, is far less understood; but, ironically, plays well into the current research in Quantum Physics.
   
   This incapacity to accept the counter intuitive, actually explains the inexplicable; mankind’s blatant disregard for his environment, his gluttonous misuse of natural resources, his failure to properly identify universal survival threats, and his apparent apathy towards the future.
   
   It further explains the budget cuts affecting our nation’s science programs, the alarming decline in math and science scores, our exit from the active space program, the transplant of Fermi lab, the cancelation of the Web telescope and fusion research.
   Mankind’s fate, in light of our Central Nervous System’s ruse, barring intervention from the scientific community, may be the eminent and unelectable human ‘Extinction Event’.
   Robert C. Wormus, Physicist, Audiologist, and Speech Pathologist
   
   
   
   

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7. 7. jfh_dragonfly@yahoo.com 09:00 PM 7/21/12

   Thanks for the detailed description of invisible photos.

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8. 8. Peter65 01:52 AM 7/22/12

   I can see the photos, though they are rather small.

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9. 9. TobyNSaunders 11:38 AM 7/22/12

   "Your brain literally enlarges the moon to fit the context." Haha, no Stephen & Susana, it does not literally enlarge the moon. It's the mental image of the moon in question.

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10. 10. almoore in reply to maxw3st 08:24 AM 7/24/12

    I concur, actual pictures would have made this article. What is the meme? Pictures or it didn't happen.

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11. 11. almoore in reply to TobyNSaunders 08:30 AM 7/24/12

    My brain has super powers, it can literally change the size of celestial objects.

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12. 12. PolishMartian 12:26 AM 7/27/12

    I agree with many of you regarding the missing photos. Was that a trick by SciAm to force non-subscribers to buy this online issue or just a horrible writing or editing job? I'm guessing the latter, especially since the ABOUT THE AUTHOR(S) section was repeated. One plug for the authors is enough; we don't need two.
    
    Not only were those errors made, but several of you had to correct a couple incorrect "facts" stated by the authors. And these authors are laboratory directors at a neurological institute and serve as Scientific American Mind's board of "advisers" (or "advisors" in the preferred American English, not traditional British English spelling)? Unless the whole article or blog was meant as an illusion, parody or satire – which I don't believe it was, because much of its information was absolutely correct – it was poorly written or illustrated and edited by people who should know better (unless SciAm Online has intern editors running the show during summer vacations).
    
    Regarding one significant optical (brain) illusion error mentioned by the authors, which was caught by and commented on by at least one other reader, anybody with an elementary knowledge of physics knows that the moon and sun look larger on the rising and setting horizons due to moonlight and sunlight passing through more layers of Earth's atmosphere then, which causes wider light refraction and different colors due to longer wavelengths of light reaching our eyes. Trees and buildings may cause additional optical-brain object comparison illusions, but that's slight compared to the refraction and wavelength until those celestial bodies are far enough above the horizon. Neurologists should know that, and if they do, they shouldn't leave it out of their description of the phenomenon.
    
    Is it my imagination or just an illusion, but I've noticed a lot more British and less American English spelling in SciAm Online articles and blogs in recent months? Also, many SciAm employee authors or editors whom I remember seeing frequently before are gone in the newsletters I receive; a few former employees just contribute blogs now. I know there were a few announced personnel changes before, but it seems that many more have occurred, voluntarily or involuntarily, with many new people replacing the previous ones. Did I miss a merger, move or something? This seems to be a sign of significant culture change, some of which I wish hadn't occurred. Has Scientific American become Scientific British or Canadian (or elsewhere else not from the U.S.)? I'm just wondering.
    

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13. 13. PolishMartian 12:45 AM 7/27/12

    @Peter65 #8: I can see five total images, of which four are definitely related to the "Small Change" and the fifth (second one down on the right) appears to be included in the group of images credited to Theo and Lars, creators of the giant wooden 50-cent euro coin. However, I couldn't identify parts of the fifth one even with zoom set at 400%.

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14. 14. PolishMartian in reply to almoore 02:43 AM 7/27/12

    @TobyNSaunders #9: You definitely caught the authors, Susana & Stephen, misstating how the brain enlarges the moon; however, @almoore #11 gave a nice sarcastic, teasing, facetious reply to you.
    
    Actually, guys, you don't have to be dealing with size illusions to do what almoore said. Not only can your super-powered brain (mind, consciousness or thought, dreams and imagination) change the size of celestial (or terrestrial) objects, but you can create new celestial or terrestrial objects, quantum particles, matter, energy, forces, physical laws, dimensions, universes and travel to all those places instantaneously – faster than Scotty's transporter in Star Trek and way faster than the speed of light (no Einstein relativistic speed limit). And to your imagination – and especially your vivid dreams – it's all LITERAL.
    
    Let's let the neurologists explain THAT one! I'm not sure they or the AI researchers have gotten all the way there yet.

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15. 15. PolishMartian in reply to PolishMartian 03:49 AM 7/27/12

    Oh, while talking about changing sizes of things and creating new ones, I forgot to add one critical thing: namely, that your super-powered brain (imagination, etc.) can destroy any or all of them...slowly or instantaneously.
    
    I do hope and wish that nobody ever does the latter in a vivid dream for obvious physical and mental health reasons, but I wouldn't bet against someone (or many people) already imagining it. However, a straw poll of living organisms and rocks in all multiverses (i.e., the entire cosmos) has requested that nobody with a stupid-powered brain actually try to make that dream come true.

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16. 16. rwormus 03:09 PM 9/2/12

    The Nefarious Irishman on Human Perception
    By Robert Castleton Wormus
    
    On the subject of opening our eyes: When we open our eyes, what do we really see? Wildly oversimplified, there are two answers to this question. What our minds have 'learned ' to perceive; and the physics of the Electromagnetic Spectrum. Not surprisingly, both will astound you! First I’ll touch on physics, followed by a synopsis of Human Visual Perception.
    The Electromagnetic Spectrum is made up of light radiation ranging from Radio waves, microwaves, Infra-red waves, visible waves, Ultra-violet waves, X-rays waves, Gamma ray waves, and possibly higher energy radiation we have yet to discover. The Electromagnetic Spectrum is what is really there. What we ‘see’, or ‘perceive to see’ is a minuscule portion of what is actually reality; greater than 99.9% of the spectrum is invisible to our retinas, and therefore never reaches our visual cortex!. To put it another way, if we scale the entire electromagnetic spectrum to a 2,500 hundred mile movie reel (approximately the distance from the California-Mexico border to the Southern border of Alaska) we see one inch of the converted 64,500,000 inches in that length. We see 1/64,500,000th of what is there! I wonder what we're missing.
    Robert Wormus 310 9535939 imnubgentl@aol.com

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17. 17. rwormus 03:13 PM 9/2/12

    Part Two: Psycho physiology of Vision
    
    by Robert Castleton Wormus
    
    The physiological ramifications of this miniscule amount of perceived radiation, is further watered down by the fact that what we see is in two dimensions, and that a large amount of human perception is ‘filled in’ by the neural synapses of some 32 separate areas of the brain, and is based on past experience, not reality.
    
    The human brain weights approximately 10 pounds, 30% of its mass makes up the Cortex. With our 100 billion neurons and their electrochemical synapses we ‘piece together’ what we ‘think we see’ from past experiences. Human vision including motion, 3D, color, identification, etc are all based on previous experience and intuition.
    Without going any further into the intricate mind games we play with our vision; let me offer as evidence a recent Neuroscience experiment recently aired on Nova, the History Channel, and National Geographic Channel.
    A basketball placed on the floor of a basketball court in front of any number of observers (all with the same vantage point) will be ‘seen’ as a basketball ball sitting on the floor. Dah! But, if we now project a prerecorded shadow of a basketball (not the basketball, just the shadow of a basketball) undergoing many different maneuvers (i.e. rolling, bouncing, and even going through the hoop) close to the sitting ball, every observer will see the sitting ball disappear, and instead ‘perceive’ the ball rolling, bouncing, and arcing in the air! No matter how hard we try, we will not ‘see’ the sitting basketball. The attention center of the visual cortex is not as strong as the intuition centers based on a moving shadow.
    

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