The Mona Lisa Does Not Actually Cause the ‘Mona Lisa Effect’

Wikimedia Commons // Public Domain
Wikimedia Commons // Public Domain

Do you ever feel like you’re being watched? By a certain Leonardo da Vinci painting, perhaps? Scientists call it the Mona Lisa effect: the sense that the eyes of a figure in a painting or photograph are following you as you move around the room. But according to a new study in the journal i-Perception, the eyes in the Mona Lisa painting don’t actually fit the criteria.

The Mona Lisa effect is real—scholars have documented the phenomenon for nearly 2000 years. The effect doesn’t just depend on the direction of the painted figure’s gaze. The figure’s head position in the painting and the slant of the picture itself create specific geometric conditions in space, distorting the viewer’s perception of the painted person’s stare. The sensation can occur no matter where the viewer is in relation to the portrait.

Until now, according to researchers at Bielefeld University in Germany, no one had tested the effect on the Mona Lisa itself. Gernot Horstmann and Sebastian Loth, members of the university’s Cluster of Excellence Cognitive Interaction Technology, designed a study in which 24 participants viewed 15 different sections of the Mona Lisa painting on a monitor. A simple ruler was placed in front of the monitor, and each viewer marked the spot where they thought the gaze landed on the ruler, which indicated its angle.

An angle of zero meant a straight-at-the-viewer look. A slightly sideward gaze toward the viewer’s ear, corresponding to a 5-degree angle, would still prompt the sense of being watched. "But as the angle increases, you would not have the impression of being looked at,” Horstmann said in a statement.

After analyzing about 2000 assessments from participants, the researchers found that viewers felt the gaze of Leonardo da Vinci’s masterpiece to be at an angle of 15.4 degrees—looking off to their right-hand side, rather than directly at them.

“It is clear that the term Mona Lisa effect is nothing but a misnomer,” Horstmann said. But even though this particular phenomenon has been demystified, people's obsession with the painting will surely continue.

11 Masks That Will Keep You Safe and Stylish

Design Safe/Designer Face Covers/Its All Goods
Design Safe/Designer Face Covers/Its All Goods

Face masks are going to be the norm for the foreseeable future, and with that in mind, designers and manufacturers have answered the call by providing options that are tailored for different lifestyles and fashion tastes. Almost every mask below is on sale, so you can find one that fits your needs without overspending.

1. Multicolor 5-pack of Polyester Face Masks; $22 (56 percent off)

Home Essentials

This set of five polyester masks offers the protection you need in a range of colors, so you can coordinate with whatever outfit you're wearing.

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2. 3D Comfort Masks 5-Pack; $20 (25 percent off)

Brio

The breathable, stretchy fabric in these 3D masks makes them a comfortable option for daily use.

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3. Reusable Face Masks 2-pack; $15 (50 percent off)

Triple Grade

This cotton mask pack is washable and comfortable. Use the two as a matching set with your best friend or significant other, or keep the spare for laundry day.

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RipleyRader

Don’t let masks get in the way of staying active. These double-layer cotton masks are breathable but still protect against those airborne particles.

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5. Washable Protective Cotton Face Masks 2-pack; $13 (35 percent off)

Its All Good

Avoid the accidental nose-out look with this cotton mask that stays snug to your face.

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6. Washable 3D Masks 12-pack; $24 (44 percent off)

Elicto

With this 12-pack of protective masks, you can keep a few back-ups in your car and hand the rest out to friends and family who need them.

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7. Reusable Dust-Proof Mask with 5 Filters; $22 (45 percent off)

Triple Grade

This dust-proof mask can filter out 95 percent of germs and other particles, making it a great option for anyone working around smoke and debris all day, or even if you're just outside mowing the lawn.

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8. Reusable Fun Face Cover / Neck Gaiter (Flamingo); $20

Designer Face Covers

Channel some tropical energy with this flamingo fabric neck gaiter. The style of this covering resembles a bandana, which could save your ears and head from soreness from elastic loops. Other designs include a Bauhaus-inspired mask and this retro look.

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9. Seamless Bandana Mask; $8 (52 percent off)

Eargasm Earplugs

This seamless gaiter-style mask can be worn properly for protection and fashioned up into a headband once you're in the car or a safe space. Plus, having your hair out of your face will help you avoid touching your eyes, nose, and mouth before washing your hands.

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Design Safe

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11. Neoprene/Fleece Neck and Face Mask (Purple); $10 (66 percent off)

Its All Good

This mask will definitely come in handy once winter rolls around. It features a fleece neck, face, and ear covering to keep your mask secure and your face warm.

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Prices subject to change.

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links. If you haven't received your voucher or have a question about your order, contact the Mental Floss shop here.

Does Putting a Penny in the Microwave Really Make It Shrink?

J E Theriot, Flickr // CC BY 2.0
J E Theriot, Flickr // CC BY 2.0

It's a lesson even the worst home cooks (hopefully) know: Putting metal in the microwave is a recipe for disaster. Thanks to a viral image circulating on the web, some people may be tempted to ignore this piece of common sense in the name of experimentation. The picture shows one normal-sized penny next to three smaller pennies with the caption: "This is what happens when you put a penny in a microwave for 2 minutes." But according to Snopes, microwaving a penny won't cause it to shrink—if anything, it will just leave you with a broken microwave.

Microwave ovens heat food by bouncing microwaves around a metal box. Certain molecules, like the molecules in your leftovers, absorb these waves via dielectric loss and convert them into heat. Not all substances are compatible with microwaves, however. Metal contains high concentrations of electrons, and when microwaves hit a metallic surface, these electrons become very active and block the wave's path. Instead of absorbing into the metal, the microwaves bounce off, which can cause electrical sparks. Sometimes these sparks are strong enough to burn a hole in the oven's walls and damage the electronic equipment.

Even if you could somehow shrink coins in a microwave, the science explained above should be reason enough to resist the urge to try it at home. Anyone who tries the experiment against their better instincts will be disappointed. The photo that's been shared on social media is a hoax, with Snopes explaining that the smaller pennies likely originated in a magician's trick kit.

The post inspired some people to share false claims of their own. One response to the image showed a melted microwave that had allegedly fallen victim to the penny trick. In reality, the years-old picture came from a blogger who set their microwave on fire accidentally while heating a pot of oil. So while microwaving a penny may cause some sparks and potentially damage your appliance, a dramatic explosion isn't likely. (Please just take our word on that, too.)

[h/t Snopes]