The Next 100 Things You Need To Know About People: #109 — People Prefer Symmetry

Take any object—a photo of a face or a drawing of a circle or a seashell—and draw a line down the middle either horizontally or vertically. If the two halves on either side of the line are identical, then the object is symmetrical.

People rate symmetrical faces as more attractive. The theory is that this preference has to do with an evolutionary advantage of picking a mate with the best DNA.

Steven Gangestad (2010) at the University of New Mexico has researched symmetry and shown that both men and women rate people with more symmetrical features as more attractive. But symmetry isn’t only about faces: bodies can be more or less symmetrical, too.

So why do people find symmetry to be more attractive? Gangestad says it may have to do with “oxidative stress.” In utero, babies are exposed to free radicals that can cause DNA damage. This is called oxidative stress. The greater the oxidative stress there is, the greater the asymmetry in the face and/or body. From an evolutionary and unconscious viewpoint, people look for partners who have no DNA damage. Symmetrical features are a clue that someone has less DNA damage. As further proof, research shows that men who are rated more attractive have fewer oxidative stress chemicals in their blood.

So, when deciding what photos to use on your website, for example, choose pictures of people who are more symmetrical than less, since those people will be viewed as more attractive.

Measuring face symmetry — You can use a ruler to measure the symmetry of a face. Using the face at the top of this blog post as an example, you would:

1. Measure the distance from the left edge of D1 to the centerline.
2. Measure the distance from the right edge of D1 to the centerline. Write down the difference between the two lines. For example, if one side of D1 is .5 inch longer than the other side, write down .5.
3. Take the same measurement for D2, D3, D4, D5, and D6. It doesn’t matter which side is longer or shorter. All your difference numbers should be positive—no negative numbers.
4. Add up all the differences.
5. The higher the sum of the differences is, the more asymmetrical the face. If the sum of all the differences is 0, then the face is perfectly symmetrical. The further from zero the total is, the more asymmetrical the face.

Gender differences — Men prefer symmetry in bodies, faces, and just about everything else, including everyday items, abstract shapes, art, and nature. But research by Kathrine Shepherd and Moshe Bar (2011) showed that women prefer symmetry in faces and bodies, but not as much as men for everything else.

• If you’re designing for a primarily male audience, then pay special attention to symmetry, whether it’s in faces, bodies, natural or man-made objects, or product pages with TVs—try to use symmetrical objects and show them in an equal right/left and top/bottom view. Men will find symmetrical images most appealing.
• If you’re designing for a primarily female audience, then symmetry in faces and bodies of people is the most important. You don’t have to be as concerned with making sure all the products are symmetrically displayed.

Why do people prefer symmetry in objects? — There might be an evolutionary advantage for preferring symmetry in a mate, but why do people prefer symmetry in objects? Some researchers have proposed that the brain is predisposed to look for symmetry, and so people see symmetrical objects faster and make sense of them faster. The theory is that this visual fluency with symmetrical objects makes people feel as though they prefer the objects. They may just find them easier to see and understand. But why this is true for men and not for women remains a mystery.

What about symmetrical web page designs? — Does the research on symmetry mean that your design should always be perfectly symmetrical? If you design a symmetrical layout, then you know that people will perceive it quickly and will more likely prefer it—especially if your target audience is men. On the other hand, if you go with an asymmetrical layout, then people will most likely be surprised by it. That may grab their attention initially, but the advantage of surprise and initial attention getting may be offset by fewer people liking it.

Here’s the research:

Gangestad, Steven W., Leslie A. Merriman, and Melissa Emery Thompson. 2010. “Men’s Oxidative Stress, Fluctuating Asymmetry, and Physical Attractiveness.” Animal Behaviour 80(6), 1005–13. doi: 10.1016/j.anbehav.2010.09.003.

Shepherd, Kathrine, and Moshe Bar. 2011. “Preference for Symmetry: Only on Mars?” Perception 40: 1254–56.

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