There is, somehow, an instant attractiveness boost conferred by sunglasses. But why is it that covering up our eyes creates this effect? Believe it or not, there is an expert on the topic (it was the subject of her PhD), and UK professor Vanessa Brown explains the situation to Science of Us. The Guardian notes Brown's research spun out of her catching sight of her own reflection one day—walking into a supermarket in scruffy painting clothes but looking, she believed "quite cool," thanks to her sunglasses. That may be because, first of all, symmetry makes us look better, and sunglasses hide asymmetry around our eyes. They also suggest a more attractive bone structure: one that's "chiseled" rather than "soft."
Sunglasses also add an air of mystery. "The eyes are such a tremendous source of information," observes Brown, and without a way to view them, others are shielded from making judgements about what we're thinking or feeling—or even how intelligent we are. (Plus, Science of Us notes that research suggests mystery is hot.) Finally, Brown points to history: In their initial early-20th-century days, sunglasses were donned by daring aviators and athletes; in the '50s and '60s, Hollywood stars wore them in hopes of avoiding recognition. We still attribute that glamor to them. These days not only can shades make the wearer look cooler to the world—they can also make the world look cooler to the wearer. A new type of sunglasses called Tens aims to give the world an Instagram-like "filter," Yahoo News reports. But hey, what is coolness, anyway?