Why does nearly everyone instantly look more attractive with sunglasses on? You know you’re at least a little curious. And so was Vanessa Brown, a senior lecturer of art and design at Nottingham Trent University in the U.K. Her research focuses on the meaning we assign to everyday objects, and in her academic book that’s coming out early next year, she explores the cultural and psychological relationship between sunglasses and our modern idea of “cool”. In an e-mail to Science of Us, Brown explained what her research has uncovered about why most of us look better in shades.

Sunglasses do make your face look better. Put on a pair of sunglasses, and there’ll be instantsymmetry（对称）! The dark lenses cover up any non-symmetrical features around your eyes, and research on facial attractiveness shows a clear link between symmetry and our ideas of beauty.

Many of the snap judgments we form about people come from looking them in the eyes. “The eyes are such atremendoussource of information for the human being,” Brown explained. Eye contact helps us form judgments about someone’s intelligence, confidence, and sincerity, and sunglasses keep us literally in the dark about forming thoseperceptionsabout a person. A recent study showed that people who wore sunglasses acted more selfishly and dishonestly than those wearing eyeglasses, which, the researchers argue, suggests that sunglasses cheat us into feeling more unknown.

Sunglasses are a relatively modern everyday accessory. Sales started to pick up in the 1920s, but they didn’t becomecommonplaceuntil about two decades after that. In their early days sunglasses were primarily used during risky water and snow sports, and were also associated with new technologies like airplane travel, which made them seem “daring and thoroughly modern”.

Soon after that, Hollywood stars of the 1950s and 1960s started wearing sunglasses to defend themselves from being recognized by the public or harassed bypaparazzi（狗仔队）, whose flashbulbs would often explode violently, sometimes literally in their faces. But regardless of practicality, movie stars’ adoption of the sunglasses strengthened the link between sunglasses and attractiveness.