Size matters not. Look at me. Judge me by my size, do you? —Yoda, Jedi master

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

 
COURTESY OF THEO TVETERÅS AND LARS MARCUS VEDELER

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-size—with the strategic placement of a giant coin. Art designers Theo Tveterås and Lars Marcus Vedeler, from the Skrekkøgle group in Oslo, created the enormous 50-cent euro coin from painted and lacquered wood at a 20:1 scale.

MISS HAVISHAM’S DINING ROOM

 
COURTESY OF CARRIE M. BECKER

Miss Havisham, from Charles Dickens's Great Expectations, is an elderly spinster who was left at the altar in her youth. Crazy with grief and disappointment, dressed in her decaying wedding gown, she still awaits her one-time groom. The uneaten, long-rotted wedding feast sits covered in spiderwebs on her elegant dining-room table. A depressing picture, to be sure. But the images on this page do not depict a real room or even a studio set outfitted for a movie version of the novel. Instead they are photographs of a 1:6 scale diorama by St. Louis–born artist Carrie M. Becker. The furniture and tiny objects are from a Japanese miniatures company called Re-Ment. Becker used webbing spray for the spiderwebs. When she photographs the scene 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—such as Becker's hand—does the illusion fail.

SUPERSIZE ME

 
FROM ‘APPLYING THE HELMHOLTZ ILLUSION TO FASHION: HORIZONTAL STRIPES WON'T MAKE YOU LOOK FATTER,’ BY PETER THOMPSON AND KYRIAKI MIKELLIDOU, IN I-PERCEPTION, VOL. 2, NO. 1; 2011. USED WITH PERMISSION FROM PION LTD, LONDON www.pion.co.uk

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.

BLOWN AWAY

 
COURTESY OF JEPPE OLSEN

Objects project smaller images on our retinas as they move away from us, which can make it hard to decide if an item is truly small or just far away (as we see in this photograph). Forced perspective photography uses this ambiguity to great effect, while eliminating many of the habitual strategies that our brain uses to distinguish size from distance, such as stereopsis (our visual system can calculate the depth in a scene from the slight differences between our left and right retinal images) and motion parallax (as we move, objects closer to us move farther across our field of view than distant objects do).

TALL AND VENTI

 
ANTHONY ROSENBERG © iStock.com

Is your cuppa joe half empty or half full? It depends on your outlook—and on a little twist on the Jastrow illusion, named after Polish-born American psychologist Joseph Jastrow. In this classic illusion, two identical arches positioned in a certain configuration appear to have very different lengths. Magician Greg Wilson and writer and producer David Gripenwaldt realized that Starbucks coffee sleeves have the perfect shape for an impromptu demonstration of the Jastrow illusion, which you can use to amaze your office mates at your next coffee break.

All you need to do is align the coffee sleeves as in the accompanying photograph and—presto!—your tall cup sleeve is now venti-size! Your brain compares the upper arch's lower right corner with the lower arch's upper right corner and concludes, incorrectly, that the upper sleeve is shorter than the lower sleeve. (We thank magician Victoria Skye for her demonstration of the Jastrow illusion with Starbucks coffee sleeves.)